Seborrheic Dermatitis

Seborrheic dermatitis, where seborrheic refers to sebaceous glands, and derm refers to skin, is a common, chronic skin condition that causes red, scaly patches that are covered in yellow, shiny and oily scales. The appearance of these patches can vary with skin tone, typically appearing reddish on light skin and lighter on dark skin. The patches can appear on a number of places on the body, but are typically found on the scalp and other areas that produce oil such as on the face or creases in the arms and legs.

The cause of seborrheic dermatitis is unknown, but there are two main factors that contribute to its development: an overproduction of sebum and Malassezia, a genus of yeast that can multiply more than usual and lead to an overproduction of oil. It’s also influenced by other factors, including stress, cold weather and hormones. People with a weakened immune system also have a higher risk of developing seborrheic dermatitis. Symptoms can vary greatly in severity for different individuals. Some may experience only mild, seasonal flare-ups whilst others may have more persistent symptoms that can include itchy patches on different parts of the skin. In teenagers and adults, seborrheic dermatitis usually doesn’t disappear on its own without treatment.

Although this skin condition cannot be cured, symptoms can be managed and flare-ups can be controlled, a topic that will be discussed later in this article. Achieving control over seborrheic dermatitis largely relies on good skincare habits. Appropriate use of skincare products such as cleansers, shampoos, and moisturizers is essential, but it’s equally important to know which ingredients to look for and which to avoid. Certain components can irritate the skin or encourage the growth of Malassezia yeast, thereby worsening the condition.

Seborrheic dermatitis may be a common skin condition, but the exact causes are unknown. There are, however, a number of factors known to contribute to its development and worsen the condition.

Malassezia yeasts, sometimes known as pityrosporum, are commonly found living on the skin of the majority of the population. They colonize the skin shortly after birth and are usually well tolerated by the human immune system [1]. In some instances, however, Malassezia can interact negatively with an individual, leading to a variety of conditions including seborrheic dermatitis, pityriasis versicolour, psoriasis and Malassezia folliculitis, also known as fungal acne.

The genus of yeasts includes different species, but M. globosa and M. restricta are the two species that have been identified as the most common organisms associated with seborrheic dermatitis in particular [2]. Malassezia species require a source of lipids, including oils, in order to grow and so are typically found in areas that produce greater amounts of oil on the body including the scalp and face. This also explains why Malassezia tends to grow around puberty when there is an increase in androgens that increase sebum (oil) production [3].

Another factor that is linked to seborrheic dermatitis is an overproduction of sebum, a naturally produced oil in the skin. Every person produces sebum through a sebaceous gland found under each pore and it’s used to protect the skin and keep it healthy and hydrated. The amount of sebum varies from person to person, which leads to different skin types, including dry and oily skin.

Several factors can contribute to an overproduction of sebum, leading to oily skin, and, potentially, seborrheic dermatitis. These include:

• Dehydrated Skin. Skin that becomes dehydrated and lacks sufficient moisture has an imbalance of oil and water, causing the sebaceous glands to produce more oil in order to prevent further water loss. Dehydrated skin can become worse during hot weather as water evaporates from the skin more easily leading to a greater imbalance.

• Hormonal Imbalance. Androgens are hormones found in both men and women that help to regulate sebum production. A hormonal imbalance, which can be caused by factors like puberty or pregnancy, can lead to overproduction of sebum and result in oily skin.

• Medications. There are a number of medications that can affect a person’s hormones and potentially alter sebum production. Anti-androgens and birth control pills can reduce sebum production, whereas other medication such as anabolic steroids can increase it.

• Smoking. Smoking has been shown to increase sebum production when compared to non-smokers by approximately 3x [4].

There are a number of risk factors that can increase the development of seborrheic dermatitis. These include:

• Age. Newborns, adolescents, and adults over the age of 30 are most at risk.
• Sex. Males are more likely to develop seborrheic dermatitis [5].
• Immunodeficiency. Lymphoma, Renal transplantation, HIV-AIDS [6].
• Neurological and psychiatric disease. Parkinson disease, Stroke, Alzheimer dementia, Major depression, Autonomic dysfunction [7].
• Drugs. This can include dopamine antagonists, Immunosuppressants, Psoralen/PUVA, Lithium.
• Environmental influences. Including humidity and/or temperature (low humidity or low temperature). A study of Thai patients with seborrheic dermatitis found that seasonal factors, especially hot weather, were primary triggering factors for aggravation [8].
  
  

How To Diagnose Seborrheic Dermatitis

As a common chronic skin condition, seborrheic dermatitis is estimated to affect approximately 5% of the global population [9]. The occurrence of the condition is bimodal, usually affecting newborns in the first few months after birth as infantile seborrheic dermatitis, often known as cradle cap, and later adolescents as adult seborrheic dermatitis.

If your seborrheic dermatitis is more severe, you may experience erythematous plaques. These are elevated, solid patches of thick-crusted skin on, and around the scalp. If left untreated, the plaque could thicken, turn yellow and greasy, and a secondary infection could occur.

Individuals with darker skin might experience petaloid seborrheic dermatitis, a more severe form where lesions form around the hairline and skin discolouration occurs. Usually, the discoloured skin manifests in a ring-shaped rash.

Seborrheic dermatitis can sometimes be confused with other skin conditions such as eczema , psoriasis , rosacea or dandruff, but there are some key differences which are important to understand as treatment for these conditions can be different.

Seborrheic Dermatitis or Eczema

Both conditions share some symptoms including redness, inflammation and sometimes itching. However, seborrheic dermatitis presents with yellow, greasy patches whereas eczema usually presents with dry, red areas of the skin that are usually itchy and in severe cases it may also causes the skin to crack and bleed. Eczema typically appears around elbows, knees, hands, wrists and ankles whereas seborrheic dermatitis usually affects the scalp and other oily areas including the face.

Seborrheic Dermatitis or Psoriasis

Psoriasis is an autoimmune disorder that leads to raised red patches with thick, silvery scales, usually on the scalp, elbows and knees, but unlike seborrheic dermatitis it can also appear on the soles of feet, the lower back and palms of the hand. It can be itchy and painful, and scales are typically thicker and drier. Both conditions can be affected by cold weather, oily skin and certain medications.

Seborrheic Dermatitis or Rosacea

Rosacea presents as persistent redness, usually on the face, with visible blood vessels and can lead to thickened areas of the skin. Areas around the eyes can also be affected and the skin may start to swell.

Seborrheic Dermatitis or Dandruff

It’s a common misconception that dandruff is another word for seborrheic dermatitis, but the two are not equivalent. Dandruff presents as flaking of the scalp due to a shedding of dead skin cells and while this can be caused by seborrheic dermatitis, it can also be caused by other conditions including eczema or psoriasis. Furthermore, dandruff occurs only on the scalp and does not cause inflammation, unlike seborrheic dermatitis that can occur on other parts of the body and cause inflammation.

When it comes to treating seborrheic dermatitis, there are a wide range of natural, over-the-counter and prescription medications available. If you are unsure what would be best for you, consult with your local general practitioner or dermatologist.

Many natural ingredients have been shown to reduce symptoms and flare-ups, although they are usually less potent than over-the-counter or prescription treatments:

Azelaic Acid. Azelaic acid occurs naturally in grains such as barley, wheat and rye and is actually a by-product of Malassezia. It has anti-bacterial and anti-inflammatory properties with one study supporting the efficacy of azelaic acid for the treatment of seborrheic dermatitis [12].

Aloe Vera. A thick, short-stemmed plant that is known for its soothing and healing properties. It has been shown to improve symptoms of seborrheic dermatitis [13].

Essential Oils. Essential oils are found in all sorts of cosmetic products and are often touted for their numerous properties such as killing bacteria, reducing inflammation, improving mood and reducing nausea. Depending on the plant, they are usually derived from flowers, barks, roots, leaves and stems. Essential oils are made up of a large number of components. While some of these may benefit the skin, others might not and could exacerbate skin conditions like seborrheic dermatitis. Only one essential oil has been shown to be safe and effective for seborrheic dermatitis; tea tree oil. Derived from an Australian tree, this essential oil is generally regarded as safe and studies have shown it to be effective against Malasezzia [14] and reducing seborrheic dermatitis [15].

Green Tea Extract. This is a concentrated form of green tea, derived from the leaves of the Camellia sinensis plant. The effectiveness of bath therapy with green tea extract has been shown to be safe and effective against Malasezzia [16] and could help reduce symptoms of seborrheic dermatitis.

Honey. Honey is a sweet, yellow liquid processed by bees using nectar from flowers. It has anti-bacterial and anti-fungal properties and has been shown to reduce scaling, relieve itching and improve overall symptoms of seborrheic dermatitis [17].

Probiotics. Probiotics consist of live bacteria and yeasts, often found in milk and yogurt products or in food supplements. They contain “friendly bacteria” and can help restore the natural balance of bacteria in your gut, but some evidence has also shown that topical probiotics can increase skin ceramides, reduce skin redness and reduce scaling [18].

Sulphur. Sulphur is a non-metallic, chemical element that’s yellow and known to have a bit of a smell. It has anti-bacterial, anti-fungal and keratolytic properties. It has been shown to reduce itching and flaking associated with seborrheic dermatitis and possibly have an anti-fungal effect on Malassezia [19].

Sunlight. There is some evidence to suggest that sunlight can be beneficial for the treatment of seborrheic dermatitis [20, 21] but in some patients it has been shown to be a triggering factor [22]. In any case, it is important to apply sunscreen beforehand and reapply it every two hours. A non-comedogenic sunscreen is less likely to worsen seborrheic dermatitis.

Urea. Also known as carbamide, this is a substance formed by the breakdown of protein in the liver and filtered out of the blood and into the urine. It has been shown to improve skin barrier function and is a common moisturizer and keratolytic (breaks down the outer layers of the skin) agent. Formulations containing urea have been shown to improve symptoms in many cases involving seborrheic dermatitis, amongst other dry or scaly skin conditions [23].

These ingredients can be purchased in various forms without a prescription, but you should always read the label and consult with a healthcare professional if you have any doubts or questions.

Benzoyl Peroxide. Also known by the brand name Acnecide in the U.K., benzoyl peroxide comes as a gel or wash, usually in concentrations of 2.5% up to 10%. It is commonly used as a treatment for acne, but studies have shown it to be effective for the treatment of seborrheic dermatitis at 2.5% concentration [24]. Side effects can include dryness of the skin and irritation. It also has a bleaching effect, so it’s important to avoid contact with coloured fabrics after applying it.

Ciclopirox. This anti-fungal medication has been shown to be similarly effective as ketoconazole as a treatment for seborrheic dermatitis [25].

Climbazole. Climbazole is an imidazole anti-fungal agent used in some skincare and haircare products for the treatment of dandruff and seborrheic dermatitis. A study in 2001 showed it successfully reduced dandruff, redness and itching in 80% of participants with seborrheic dermatitis, with a mild improvement in the remaining 20% [26].

Coal Tar. Coal tar can be found in some shampoos, either as the main ingredient or combined with others, to help prevent itching, scaling and flaking. There is some evidence to suggest its effectiveness in treating seborrheic dermatitis [27], although it can be irritating for some as well as having an unpleasant smell. Some components of coal tar, including benzene and naphthalene, have been identified as carcinogenic.

Ketoconazole. Also known by different brand names, this is an anti-fungal medication used to treat skin infections caused by yeast, usually available as a cream or shampoo. It has been shown to be as effective as a 1% hydrocortisone cream for seborrheic dermatitis [28] and more effective in reducing dandruff than ciclopirox olamine [29]. It has shown to be not only effective in clearing the scalp of seborrheic dermatitis, but also in preventing relapse when used once weekly [30].

Piroctone Olamine. This active ingredient has anti-bacterial and anti-fungal properties, helping to inhibit the growth of Malassezia. It has been shown to effectively treat seborrheic dermatitis [31] and control symptoms of flaking, itching and redness. It is well-tolerated by most individuals and often used in conjunction with other ingredients.

Salicylic Acid. Salicylic acid is a relatively common skincare ingredient known for its exfoliating properties. It is a beta hydroxy acid that dissolves bonds between skin cells to help remove old, dead tissue, reducing the build up of scales and flakes. It also has mild anti-inflammatory properties to help reduce redness and swelling, as well as mild anti-fungal properties that may inhibit the growth of Malassezia.

Selenium Sulfide. Selenium sulfide is an active ingredient in some shampoos, usually in concentrations of 1% to 2.5%, with anti-fungal properties. It’s used to manage dandruff and seborrheic dermatitis by reducing the production of sebum and slowing down the growth of skin cells to prevent flaking. A 2013 study found that, compared to a 2% ketoconazole shampoo, selenium sulfide had a significantly higher number of adverse effects. However, both were shown to be similarly effective for the treatment of dandruff when compared to a placebo [32].

Zinc Pyrithione. Zinc Pyrithione has long been used for the treatment of dandruff and seborrheic dermatitis and shown to reduce their symptoms [25]. Until recently, it was found in many popular anti-dandruff shampoos. However, as of 2022, it has been banned in both the EU and U.K.

The following medications can only be prescribed from a GP or dermatologist and are usually reserved for more severe cases of seborrheic dermatitis, or when over-the-counter treatments do not produce the desired results.

Topical Steroids / Corticosteroids. Topical steroids may be prescribed by a GP for those suffering from symptoms of seborrheic dermatitis. In 2011, a study compared the effects of a corticosteroid shampoo containing clobetasol propionate with ketoconazole and found it to reduce symptoms far better in comparison [34]. They have some negative long-term effects, including high blood pressure
and an increased risk of infections. Therefore, it’s important to discuss this with your GP first.

Topical Calcineurin Inhibitors. These are different kinds of treatments that alter the immune system rather than provide anti-fungal properties. They have been shown to be effective at both treating seborrheic dermatitis and reducing the severity of symptoms if they reoccur after treatment stops. However, they may have some adverse effects, including mild burning and irritation [35].

When treating seborrheic dermatitis, it’s just as important to know what to avoid applying to your skin as it is to understand what you should apply. Malassezia yeasts play a crucial role in the onset of seborrheic dermatitis, so it’s recommended to steer clear of ingredients that might nurture Malassezia. Overproduction of sebum can also induce flare-ups, so various oils and comedogenic (pore-clogging) ingredients should ideally be avoided.

The following are some examples of the types of ingredients to be careful of, followed by a list of some of the most common ingredients found in everyday skincare products to look out for. It should be noted that the presence of some of these ingredients doesn’t necessarily render a product unsuitable. This also depends on other factors such as the concentration of the particular ingredient (the manufacturer does not have to disclose this information, but ingredients have to be listed from highest to lowest concentration if they exceed 1%), how the ingredient is used, and whether there are other beneficial ingredients within the product.

Alcohols. While not all alcohols are harmful in relation to seborrheic dermatitis, those derived from oils containing fatty acids within the C11-C24 carbon range may feed Malassezia.

Artificial Dyes. Like fragrances, artificial dyes can cause irritation and lead to inflammation.

Coconut Oil. While coconut oil can be beneficial for many skin conditions due to its
anti-inflammatory and anti-bacterial properties, it may not be suitable for people with seborrheic dermatitis. Coconut oil primarily comprises lauric acid, a fatty acid within the C11-24 range that can feed Malassezia.

Comedogens. Comedogenic ingredients can clog pores. Typically, they are given a rating from 0, meaning they are entirely non-comedogenic and will not clog the pores, to 5, where there is a high likelihood of pore-clogging. Generally, ingredients with a rating of 2 or less can be considered mostly non-comedogenic. The use of highly comedogenic products may exacerbate seborrheic dermatitis, so care should be taken when selecting such products. It’s advisable to avoid constantly covering up inflamed skin patches with heavy foundation or concealer as this can clog skin pores.

Esters. Esters are organic compounds formed by the reaction between an alcohol and an organic acid. Widely used in the cosmetics industry for their pleasing scents or as solvents, they can be easily identified in cosmetic product ingredients lists as they end in ‘ate’, such as isopropyl myristate or glyceryl stearate. Depending on the fatty acids and alcohols that form the esters, some of these may feed Malassezia. Many of these can also be found in the list below.

Fatty Acids. Malassezia is known to metabolise (feed on) specific types of fatty acids, in particular those with longer carbon chains ranging from C11 to C24 [36]. Many oils contain fatty acids in this range, but not all. These can be found in the list below.

Fragrances. Fragrances may or may not feed Malassezia depending on their origin, but they can be irritating for people with sensitive skin, so they are best avoided.

Parabens. Occasionally used as preservatives in cosmetic products, parabens can irritate sensitive skin, so they are best avoided. Their use in cosmetics has significantly decreased in recent years.

Phthalates. These are a group of chemicals commonly used to make plastic more durable but also act as a binding agent or a solvent. They can irritate the skin and have been connected to a number of health issues so are best avoided. They are usually labelled as fragrances.

Polysorbates. Polysorbates are nonionic surfactants derived from alcohol and fatty acids, frequently used in cosmetic products. They help mix oil and water-based ingredients together, forming stable emulsions which are useful in creams and lotion formulations. Polysorbate 20, 40, 60, and 80 are derived from lauric, palmitic, stearic, and oleic acid, respectively, which can feed Malassezia.

Silicones. Certain forms of silicones can trap dirt and bacteria in your pores, which can exacerbate skin conditions.

Sulphates. Sulphates can irritate those with sensitive skin so avoiding them could prevent further irritation or inflammation. For example, a 1992 study found that people with seborrheic dermatitis are more susceptible to irritation induced by sodium lauryl sulphate (SLS) [37].

The Blacklist

You can use the following list as a guide to determine if any skincare products you use contain ingredients that could potentially aggravate seborrheic dermatitis. Please note that other factors should be taken into consideration, such as the concentration of said ingredients, other ingredients in the product, and the overall composition.

Polysorbates:

• Polysorbate 20
• Polysorbate 40
• Polysorbate 60
• Polysorbate 80

Esters derived from fatty acids in range C11-C24:

• Isopropyl Myristate
• Ethylhexyl Palmitate
• Glyceryl Stearate – (this is used in a low concentration in our anti-dandruff shampoo as an emulsifier and to help condition the hair)
• Cetyl Palmitate
• Butyl Stearate
• Isopropyl Palmitate
• Cetearyl Ethylhexanoate
• Decyl Oleate
• Propylene Glycol Dicaprylate/Dicaprate
• Isostearyl Isostearate
• Caprylic/Capric Triglyceride
• Dicaprylyl Ether
• Ethylhexyl Cocoate
• Lauryl Lactate
• Pentaerythrityl Tetraisostearate
• Isocetyl Stearate
• Neopentyl Glycol Diheptanoate
• Behenyl Behenate
• Stearyl Heptanoate
• Myristyl Lactate
• Diisopropyl Sebacate
• Tridecyl Stearate
• Lauryl Laurate
• Stearyl Palmitate
• Myristyl Myristate
• Isostearyl Palmitate
• Octyldodecyl Stearoyl Stearate
• Myristyl Laurate
• Isopropyl Isostearate
• Glyceryl Caprylate/Caprate
• Decyl Stearate
• Dicaprylyl Carbonate
• PPG-2 Myristyl Ether Propionate

Fatty Acids:

• Undecylenic acid (C11:0)
• Lauric acid (C12:0)
• Tridecanoic acid (C13:0)
• Myristic acid (C14:0)
• Pentadecanoic acid (C15:0)
• Palmitic acid (C16:0)
• Margaric acid (C17:0)
• Stearic acid (C18:0)
• Nonadecanoic acid (C19:0)
• Arachidic acid (C20:0)
• Heneicosanoic acid (C21:0)
• Behenic acid (C22:0)
• Tricosanoic acid (C23:0)
• Lignoceric acid (C24:0)

Sulphates:

• Sodium Lauryl Sulfate (SLS)
• Sodium Laureth Sulfate (SLES)
• Ammonium Lauryl Sulfate (ALS)
• Ammonium Laureth Sulfate (ALES)
• Sodium Coco Sulfate (SCS)
• Sodium Lauroyl Sarcosinate
• Sodium Lauroyl Methyl Isethionate (SLMI)
• Sodium Lauroyl Glutamate
• Sodium Lauroyl Lactylate (SLL)
• Sodium Cocoyl Sarcosinate
• Sodium Lauryl Sulfoacetate (SLSA)
• Disodium Laureth Sulfosuccinate (DLES)
• Disodium Lauryl Sulfosuccinate (DLS)

Alcohols:

• Undecyl Alcohol (C11)
• Lauryl Alcohol (C12)
• Tridecyl Alcohol (C13)
• Myristyl Alcohol (C14)
• Pentadecyl Alcohol (C15)
• Cetyl Alcohol (C16)
• Stearyl Alcohol (C18)
• Arachidyl Alcohol (C20)
• Behenyl Alcohol (C22)
• Erucyl Alcohol (C22:1)
• Lignoceryl Alcohol (C24)

Fragrances:

• Linalool
• Limonene
• Geraniol
• Citronellol
• Coumarin
• Alpha-isomethyl ionone
• Benzyl salicylate
• Hexyl cinnamal
• Eugenol
• Citral
• Farnesol
• Benzyl benzoate
• Hydroxycitronellal
• Cinnamyl alcohol
• Amyl cinnamal
• Anisyl alcohol
• Isoeugenol
• Benzyl cinnamate
• Methyl anthranilate
  
  

Are Seborrheic Dermatitis and Dandruff the Same Thing?

NO. While these two terms are sometimes used interchangeably, they represent different conditions. Seborrheic dermatitis is a skin condition that can affect various areas of the body. Dandruff, on the other hand, is specific to the scalp and can be a symptom of seborrheic dermatitis or another skin condition such as eczema.

Does Seborrheic Dermatitis Only Affect the Scalp?

NO. Although seborrheic dermatitis frequently occurs on the scalp due to the presence of oil-producing glands, it can appear on several other areas of the body, typically those rich in oil-producing glands.

Can Stress Affect Seborrheic Dermatitis?

YES. Stress is often linked to seborrheic dermatitis flare-ups and in a 2007 study, a likely connection was confirmed [38]. Therefore, managing stress could be an essential part of symptom management. This might involve prioritizing quality sleep, practicing relaxation techniques, and engaging in regular physical activity.

Does Seborrheic Dermatitis Cause Hair Loss?

NO. Seborrheic dermatitis can cause itching and may lead to excessive scratching which can result in hair breakage and temporary hair loss. However, these effects are not directly caused by seborrheic dermatitis itself.

Is Seborrheic Dermatitis Caused by a Bad Diet?

NO. As previously discussed, the primary factors influencing seborrheic dermatitis include overproduction of oil and the presence of Malassezia yeast. Although a 2019 study showed a correlation between a high fruit intake and reduced seborrheic dermatitis, compared to a ‘Western’ diet rich in fats which was associated with increased seborrheic dermatitis in females [39], another smaller study concluded that dietary factors do not directly cause seborrheic dermatitis [40].

Seborrheic dermatitis is a common, chronic skin condition affecting a significant number of people, characterized by red, scaly patches with silvery scales that can sometimes be itchy. While the precise cause remains somewhat elusive, the connection between seborrheic dermatitis, overproduction of sebum, the Malassezia yeast, and some underlying health conditions is evident.

Numerous treatments, ranging from natural remedies to over-the-counter medications and prescription drugs, have demonstrated varying degrees of efficacy. Additionally, certain ingredients are known to potentially worsen the condition, so avoiding these can also be instrumental in reducing symptoms and preventing flare-ups.

Although seborrheic dermatitis is generally a lifelong condition, except in the case of cradle cap, most individuals can effectively manage their symptoms through a thoughtful skincare routine and a healthy lifestyle.

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