Pink or red skin on the scalp may be caused by a variety of underlying conditions or disorders. These can include psoriasis, seborrhoeic eczema and lichen planus, according to WebMD.
Psoriasis is an incurable condition that generally recurs throughout a patient's lifetime. It often begins as a pink or red rash that can occur in a number of areas on the body, especially the scalp. It is often accompanied by flaking skin.
Seborrhoeic eczema is a form of dermatitis on the scalp and upper body that can be chronic or recurring. Treatment is generally in the form of medicated shampoo, steroid creams or ointments.
Lichen planus is a relatively rare condition with an unknown cause, but it is thought to be linked to stress. It can cause pink or red patches on the skin as well as hair loss.
Other causes of pink scalp can include unspecific rashes and adverse drug reactions.