What is seborrhoeic dermatitis?

Seborrhoeic dermatitis, the cause of dandruff, is a skin condition that causes greasy scales mainly on the scalp, ears, face and upper body. The skin in these areas is rich in oil glands, also known as the sebaceous glands. Unlike some other types of dermatitis, the seborrhoeic form does not itch.

Although seborrhoeic dermatitis can appear at any age, it mostly occurs in adolescents and young adults. In adults, seborrhoeic dermatitis of the scalp produces dandruff. When it occurs on a baby's scalp it is called 'cradle cap'.

Dandruff

Scaling of dead skin cells from the scalp.

Sebaceous glands

Small glands located in the skin throughout the body (although not usually on the palms of the hands or soles of the feet). They produce an oil called sebum that helps to lubricate the skin, prevent evaporation of sweat and maintain body heat.

Causes

Although the exact cause of seborrhoeic dermatitis is unknown, an immune reaction to the Malassezia fungal yeast family is thought to be involved. It is normal for these yeasts to live in the skin's natural oil (sebum) without causing problems, along with bacteria and other organisms.

In certain individuals, though, it has been suggested that these yeasts produce toxic substances, resulting in skin irritation and inflammation. However, seborrhoeic dermatitis is not considered an infection in its own right, and the condition is not passed on from one person to another.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Inflammation

A body’s protective immune response to injury or infection. The accumulation of fluid, cells and proteins at the site of an infection or physical injury, resulting in swelling, heat, redness, pain and loss of function.

Yeast

A single-celled fungus that can causes infections. Candida, the cause of thrush, is an example of a yeast.

Risk factors

Risk factors for seborrhoeic dermatitis include:

  • Being an adolescent or young adult, when the oil glands are most active;
  • Being male;
  • Obesity;
  • Frequent exposure to extreme weather conditions;
  • Also having certain other medical conditions, such as HIV/AIDSParkinson's diseasestroke, some cancers, Down syndrome and alcoholic pancreatitis;
  • A weakened immune system, and;
  • Lifestyle factors, such as heavy alcohol intake, poor nutrition, infrequent skin cleaning, stress or fatigue.

Immune system

The organs and cells involved in protecting the body against infection.

Pancreatitis

Inflammation of the pancreas.

Signs and symptoms

Seborrhoeic dermatitis usually appears where the skin is oily or greasy. Symptoms may flare up and then settle down in cycles over time. Common signs and symptoms include:

  • Red, greasy and inflamed skin;
  • Scaly patches or thick crusts on the scalp or face, particularly along the hairline, on the bridge or in the creases of the nose and inside the ears;
  • Yellow or white flakes (dandruff) on the scalp, or in the hair, eyebrows, moustache or beard;
  • Flaky yellow or white scales on other areas, including the chest, armpits and groin, and;
  • Skin soreness.

Seborrhoeic dermatitis can occur on the scalp in babies as a thick, yellow and crusty patch, sometimes accompanied by skin cracks behind the ears, red blisters on the face, or nappy rash. This condition is known as cradle cap. In older children, a thick, scaly area measuring about 1-2 centimetres across can develop on the scalp.

  • Sites at which seborrhoeic dermatitis generally occurs.
    Sites at which seborrhoeic dermatitis generally occurs.
  • Facial appearance of seborrheic dermatitis.
    Facial appearance of seborrheic dermatitis.

Dandruff

Scaling of dead skin cells from the scalp.

Methods for diagnosis

A doctor will usually diagnose seborrhoeic dermatitis by looking closely at the skin. As the condition is sometimes a sign of another underlying issue, your doctor may also ask you questions about your medical history.

If the condition has not responded to treatment, a small skin sample (biopsy) may be taken to look for infection, or rule out other contributing factors. Additional tests may be recommended if another condition is suspected.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Types of treatment

As there is no cure for seborrhoeic dermatitis, one or more treatments may be prescribed by a doctor with the aim of managing symptoms and preventing flare-ups. The treatment plan will most likely depend on how severe the symptoms are and where on the body they appear.

Adults

For adults, treatment options usually include the following.

Self care

To remove skin oils and improve the general condition of the skin, regular washing with soap and water will most likely be recommended. A doctor may also encourage outdoor activities, particularly in the summer, to improve the condition through safe, moderate exposure to sunlight.

Creams

In mild cases, a antifungal cream may be prescribed for direct application to the skin. These creams commonly contain medications such as ketoconazole or clotrimazole, which fight the Malassezia family of fungi. Alternatively, they may contain other medicated substances such as salicyclic acid, sulphur or coal tar.

When symptoms are more severe, a mild corticosteroid cream, such as hydrocortisone or betamethasone, may be prescribed. However, these corticosteroid medications are not usually used as a long-term treatment option due to side effects.

Shampoos

For seborrhoeic dermatitis of the scalp, a medicated shampoo may be prescribed to treat symptoms and clear dandruff. The ingredients in these shampoos are similar to those found in the antifungal creams or other medicated substances, such as selenium sulphide or zinc pyrithione. Switching between shampoos may be recommended if one type works for a period then loses its effectiveness.

Babies

In babies, seborrhoeic dermatitis of the scalp (cradle cap) tends to clear up with no treatment when the child is between six months and one year of age. However, if treatment is necessary, a doctor may suggest daily cleansing with a mild baby shampoo, or gently brushing away any skin scales once they have softened. Care should be taken to avoid breaking the skin, which can lead to infection.

If symptoms do not clear or the baby seems uncomfortable, a doctor may prescribe a milder version of an adult shampoo or cream.

Corticosteroid

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Dandruff

Scaling of dead skin cells from the scalp.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Potential complications

The most common complications of seborrhoeic dermatitis are infection of the skin with bacteria or viruses, or psychological issues such as depression, low self-esteem or embarrassment. In rare cases, symptoms may become severe, or develop into a condition called erythroderma, which is the term used to describe intense and widespread skin redness.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Prognosis

Even though seborrhoeic dermatitis is often a long-term condition with no cure, the outlook is generally quite good when symptoms are managed effectively. By paying careful attention to skincare routines and reacting quickly to flare-ups, the severity of the condition can be limited.

In babies, symptoms often resolve without treatment between the ages of six months and one year. It is also possible for seborrhoeic dermatitis to clear without treatment in adolescents and adults, but usually it lasts for years. However, complications are not usually an issue and the condition responds well to treatment.

Prevention

Seborrhoeic dermatitis cannot be completely prevented from occurring in the first place. Things you can do to lower your risk of seborrhoeic dermatitis include maintaining a healthy diet, reducing your alcohol consumption, maintain good washing habits and skin care, and avoiding stress and fatigue if possible.

If you have already had seborrhoeic dermatitis, once symptoms have been cleared with treatment you can prevent future flare-ups by maintaining good washing habits to clean oil and any traces of fungus from the body. Your doctor may also suggest continued use of antifungal creams and shampoos as a preventative measure.