Dandruff signs and symptoms may include:

• Skin flakes on your scalp, hair, eyebrows, beard or mustache, and shoulders
• Itchy scalp
• Scaly, crusty scalp in infants with cradle cap

The signs and symptoms may be more severe if you're stressed, and they tend to flare in cold, dry seasons.

When to see a doctor

Most people with dandruff don't require a doctor's care. See your primary care doctor or a doctor who specializes in skin conditions (dermatologist) if your condition doesn't improve with regular use of dandruff shampoo.

Dandruff may have several causes, including:

• Irritated, oily skin
• Dry skin
• A yeastlike fungus (malassezia) that feeds on oils on the scalps of most adults
• Sensitivity to hair care products (contact dermatitis)
• Other skin conditions, such as psoriasis and eczema

Almost anyone can have dandruff, but certain factors can make you more susceptible:

• Age. Dandruff usually begins in young adulthood and continues through middle age. That doesn't mean older adults don't get dandruff. For some people, the problem can be lifelong.
• Being male. Dandruff is more prevalent in males than in females.
• Certain illnesses. Parkinson's disease and other diseases that affect the nervous system also seem to increase risk of dandruff. So does having HIV or a weakened immune system.

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

The itching and flaking of dandruff can almost always be controlled. For mild dandruff, first try regular cleansing with a gentle shampoo to reduce oil and skin cell buildup. If that doesn't help, try a medicated dandruff shampoo. Some people can tolerate using a medicated shampoo two to three times a week, with regular shampooing on other days if needed. People with drier hair would benefit from less frequent shampooing and a moisturizing conditioner for the hair or scalp.

Hair and scalp products, both medicated and nonmedicated, are available as solutions, foams, gels, sprays, ointments and oils. You may need to try more than one product to find the routine that works for you. And you'll likely need repeated or long-term treatment.

If you develop itching or stinging from any product, stop using it. If you develop an allergic reaction — such as a rash, hives or difficulty breathing — seek immediate medical attention.

Dandruff shampoos are classified according to the medication they contain. Some are available in stronger formulations by prescription.

• Pyrithione zinc shampoos (DermaZinc, Head & Shoulders, others). These contain the antibacterial and antifungal agent zinc pyrithione.
• Tar-based shampoos (Neutrogena T/Gel, Scalp 18 Coal Tar Shampoo, others). Coal tar slows how quickly skin cells on your scalp die and flake off. If you have light-colored hair, this type of shampoo may cause discoloration. It can also make the scalp more sensitive to sunlight.
• Shampoos containing salicylic acid (Jason Dandruff Relief Treatment Shampoo, Baker P&S, others). These products help eliminate scaling.
• Selenium sulfide shampoos (Head & Shoulders Intensive, Selsun Blue, others). These contain an antifungal agent. Use these products as directed and rinse well after shampooing, as they can discolor the hair and scalp.
• Ketoconazole shampoos (Nizoral Anti-Dandruff). This shampoo is intended to kill dandruff-causing fungi that live on your scalp.
• Fluocinolone shampoos (Capex, Derma-Smoothe/FS, others). These products contain a corticosteroid to help control itching, flaking and irritation.

If one type of shampoo works for a time and then seems to lose its effectiveness, try alternating between two types of dandruff shampoos. Once your dandruff is under control, try using the medicated shampoo less frequently for maintenance and prevention.

Read and follow the directions on each bottle of shampoo you try. Some products need to be left on for a few minutes, while others need to be rinsed off quickly.

If you've used medicated shampoo regularly for several weeks and still have dandruff, talk to your doctor or dermatologist. You may need a prescription-strength shampoo or a steroid lotion.

You can take steps to reduce your risk of developing dandruff or to control it:

• Learn to manage stress. Stress affects your overall health, making you susceptible to a number of conditions and diseases. It can even help trigger dandruff or worsen existing symptoms.
• Eat a healthy diet. A diet that provides enough zinc, B vitamins and certain types of fats may help prevent dandruff.
• Develop a hair and scalp care routine that suits you. If you tend to have an oily scalp, daily shampooing may help prevent dandruff. Gently massage your scalp to loosen flakes. Rinse thoroughly. If your hair tends to be dry and your scalp is sensitive, shampoo less frequently and condition your scalp between washings (Design Essentials, Melanin Haircare, ScalpBliss).
• Get a little sun. Sunlight may be good for controlling dandruff. But because exposure to ultraviolet light damages your skin and increases your risk of skin cancer, don't sunbathe. Instead, just spend a little time outdoors. And be sure to wear sunscreen on your face and body.
• Limit hair-styling products. Hair-styling products can build up on your hair and scalp, making them oilier.

Tea tree oil is included in a number of shampoos, but there is no strong evidence to support its use for dandruff control. It comes from the leaves of the Australian tea tree (Melaleuca alternifolia) and has been used for centuries as an antiseptic, antibiotic and antifungal agent. The oil may cause allergic reactions in some people.

You don't need any special preparations for an appointment to diagnose dandruff. Your doctor will likely be able to diagnose your dandruff simply by looking at your scalp and skin. If you've started using any new hair care products, bring the bottles with you to your appointment or be prepared to tell your doctor about them, which help in determining the cause of your dandruff.