Dandruff is a common condition that causes small pieces of dry skin to flake from the scalp. It isn't contagious or harmful. But it can be embarrassing and difficult to treat.

You can treat mild dandruff with gentle, regular shampooing. If that doesn't help, you may need to use a special medicated shampoo.

There is no cure for dandruff. Even if you treat it, the symptoms may come back later. But with treatment, most people can manage the symptoms.

Dandruff is a mild form of seborrheic dermatitis, a skin condition that mainly affects your scalp.

Dandruff symptoms may include:

• Skin flakes on your scalp, hair, eyebrows or shoulders.
• Itchy scalp.
• Scaly, crusty scalp in infants. This also is called cradle cap.

Dandruff may get worse when you're stressed or during cold, dry weather.

When to see a doctor

Dandruff usually doesn't need medical treatment. But if it doesn't get better with regular use of dandruff shampoo, see your healthcare professional.

Dandruff may have several causes, including:

• Irritated, oily skin.
• Dry skin.
• A type of fungus called malassezia that lives on the scalps of most adults and feeds on natural oils.
• Sensitivity to hair care products. This is called contact dermatitis.
• Other skin conditions, such as psoriasis and eczema.

Almost anyone can have dandruff. Some factors can make you more likely to have it:

• Age. Dandruff often starts in young adulthood and lasts through middle age. But older adults can have it too. For some people, it never goes away.
• Sex assigned at birth. Dandruff is more common in males.
• Certain illnesses. Conditions that affect the nervous system, such as Parkinson's disease, increase the risk of getting dandruff. Having HIV or a weakened immune system also can make dandruff more likely.

A healthcare professional often can diagnose dandruff simply by looking at your hair and scalp.

You usually can treat mild dandruff at home. Start by washing your hair more often with a gentle shampoo. This helps clean away extra oil and dead skin from the scalp.

If that doesn't help, try a medicated dandruff shampoo. Some people can tolerate using dandruff shampoo 2 to 3 times a week. If you have curly, coiled or textured hair, you may want to use it less often.

If a shampoo causes itching, burning or stinging, stop using it. If you have an allergic reaction to any product, such as a rash, hives or trouble breathing, get medical help right away.

You can buy medicated dandruff shampoos without a prescription. Different shampoos work in different ways depending on the ingredients. Some ingredients help kill or slow the fungus that may cause dandruff. These include:

• Ketoconazole (Nizoral Anti-Dandruff).
• Pyrithione zinc (Head & Shoulders, Jason Anti-Dandruff, others).
• Selenium sulfide (Selsun Blue, Head & Shoulders, others).

Other shampoos have ingredients that help with itching, scaling and flaking. These include:

• Salicylic acid (Denorex Extra Strength, Neutrogena T/Sal, others).
• Coal tar (Neutrogena T/Gel, DHS Tar, others).

Some shampoos, such as those with coal tar, may darken or stain light-colored hair. They also can make your scalp more sensitive to sunlight.

Read and follow the directions on each bottle of shampoo you try. Be sure to apply the shampoo directly to the scalp and gently rub it in. Most dandruff shampoos need to sit on the scalp for several minutes or more before you rinse them out.

Try using different shampoos, and switch between them each time you wash your hair. If one shampoo doesn't help, try switching to another one with different ingredients. When your dandruff gets better, you can use dandruff shampoo less often. But you may want to keep using it at least once a week to help keep dandruff from coming back.

If you've used dandruff shampoo for a few weeks and it isn't helping, see your healthcare professional or a skin specialist. You may need a prescription-strength shampoo or steroid lotion.

You can do a few simple things to help prevent dandruff or keep it under control:

• Manage stress. Stress can affect your body in many ways. It may even cause dandruff or make it worse. Find ways to relax, such as deep breathing, exercising or spending time on a hobby you enjoy.
• Take care of your hair and scalp. Find a hair care routine that works for you. If you have fine or naturally straight hair or an oily scalp, wash your hair often. If you have textured or naturally curly or coiled hair, wash your hair when needed. When you wash your hair, gently massage the scalp to loosen flakes. Make sure to rinse well.
• Get a little sun. A few minutes of sunlight each day may help with dandruff. But don't stay outside too long because too much sun can damage your skin. Always use sunscreen on your face and body.
• Use fewer styling products. Hair gels, sprays and other products can build up on your scalp. This can make your scalp oily and cause more dandruff.

Many shampoos contain tea tree oil. The oil comes from the leaves of the Australian tea tree, called Melaleuca alternifolia. There is no strong evidence that tea tree oil helps with dandruff. It may cause allergic reactions in some people.

You don't need to do anything special to prepare for an appointment about dandruff. Your healthcare professional can usually tell if you have dandruff just by looking at your scalp and skin. If you've been using any new shampoos or hair products, bring the bottles with you or be ready to tell your healthcare professional about them. This can help your healthcare team figure out what's causing your dandruff.