Does seborrheic dermatitis spread?

Can it appear beyond the scalp?

Yes. Seborrheic dermatitis usually affects oily areas, including the scalp, eyebrows, beard, ears and creases around the nostrils. It can also affect the chest, upper back and skin folds. Dandruff can be the mildest form, but seborrheic dermatitis also causes inflammation: swelling and changes in skin colour. On darker skin, patches can look pink, slightly purple or lighter than nearby skin; on lighter skin, they often look red and raised.12

Why do patches appear in different places?

The exact cause is uncertain. Malassezia, a yeast that normally lives on everyone's skin, is thought to play a role when it grows excessively and triggers a skin reaction. The yeast grows well in oily areas, which helps explain the pattern of affected sites. Having yeast involved does not make seborrheic dermatitis contagious. Dandruff is not caused by poor hygiene, either, although flakes can become more noticeable without regular hair washing.13

Does a new patch mean it is getting worse?

Seborrheic dermatitis can come and go, and a returning rash does not mean you caught it again. Teenagers and adults can have recurring flares for years. Stress and cold, dry weather can worsen symptoms; flares often occur in winter and early spring. Treatment can reduce itching and scaling and sometimes clear the rash, but there is no cure. A spreading or changing rash still deserves assessment if the diagnosis is uncertain.2

What should you do about new patches?

1. 1For mild scalp dandruff, try a dandruff shampoo containing ketoconazole, coal tar or salicylic acid. A pharmacist can explain how to use the product.
2. 2Use the shampoo as directed and leave it on for the instructed contact time. Frequency depends on the product and hair type: some plans use shampoo 2 to 3 times weekly for straight or wavy hair, or once weekly for curly or tightly coiled hair.
3. 3Allow up to 4 weeks to assess whether a dandruff shampoo helps. If one does not work, another active ingredient can be worth trying.
4. 4Have new face or body patches assessed rather than assuming every flaky patch is seborrheic dermatitis. Treatment can include an antifungal cream or medication that reduces inflammation.
5. 5Once symptoms are controlled, follow the maintenance plan. Some people continue dandruff shampoo once weekly to help prevent flares.

Different dandruff shampoos work differently, despite sharing a job title on the bottle.4

A dermatologist can also recommend dandruff shampoo for the beard, face or another affected area. Follow those specific directions. Medicated creams, gels and foams can have different application schedules, even when they contain the same medicine. If prescribed ciclopirox shampoo irritates your scalp, stop using it and tell your dermatologist.4

In babies, seborrheic dermatitis is usually called cradle cap and generally clears within weeks to months. Dandruff shampoo is not recommended for children. Baby shampoo and gentle removal of loosened scales are options for cradle cap.4

What if it affects your eyelids?

Seborrheic dermatitis can cause blepharitis, meaning inflamed eyelids, with flakes around the eyelashes, soreness or a gritty feeling. Blepharitis is also not contagious. Clean affected eyelids twice daily and avoid contact lenses and eye makeup while symptoms are present. Eye pain, vision changes or very red eyes need urgent medical assessment.5

When should you see a doctor?

Several conditions can cause similar flaky patches, so choosing a treatment by appearance alone asks the bathroom shelf to do diagnostic work.2

Arrange an assessment if the rash worsens, affects daily life, or does not improve with treatment. For scalp dandruff, seek help if symptoms persist after at least 4 weeks of dandruff shampoo. Painful, swollen skin or skin draining fluid needs medical attention because these can signal infection. Avoid scratching: breaking the skin can cause bleeding and infection. Before the appointment, note where patches appear and when symptoms flare.123