An itchy scalp is very common, particularly in adults, and may or may not be due to any disease. If there is absolutely nothing visible accompanying an itchy scalp or just a few flakes of dry skin, you may have a mild case of dandruff.
Dandruff (seborrheic dermatitis) is the most common cause of an itchy rash on the scalp in adults and tends to affect the whole scalp; psoriasis is another common cause of itchy scalp and is often found just on the back of the scalp. Both conditions, dandruff and scalp psoriasis, have patches of redness and scaling and may also affect the ear area. People with psoriasis may also have other body areas affected, commonly the elbows and knees.
Inflammation or bacterial infection of the hair opening (follicle) causes folliculitis, with one or more pimples or scabs in the scalp or beard area; pseudofolliculitis barbae, also known as "razor bumps," is usually found in the beard and neck area; and acne keloidalis nuchae, commonly known as "hair bumps," is found on the back of the scalp. Both pseudofolliculitis barbae and acne keloidalis nuchae are most often seen in black men. Folliculitis caused by a bacterial infection may be associated with small sores or pimples in the nostrils or other body regions.
Contagious skin conditions causing itchy scalp and neck include head lice (pediculosis capitis) and scalp ringworm (tinea capitis), which are most often seen in children. Head lice are often hard to see, but their eggs (nits) can be noted stuck to the hair shaft, usually in the area behind the ears or the back of the neck. Scalp ringworm (caused by several types of fungi) can show up in several ways, depending upon the type of fungus and the way the immune system of the infected person reacts. Sometimes only a bald patch of broken-off hairs is seen, while other times there are red pimples or scaly patches. Rarely there may be large areas of pus, swelling, and baldness.
Click any of the images below to learn more about conditions relating to an itchy scalp.