<unk>  is not caused by bacterial infection, allergy or poor hygiene.<unk>  is also not contagious. Doctors do not agree on what causes<unk> , but the two most common hypotheses are fungal infection and overactive sebaceous glands.<unk>  is an inflammatory condition. Possibly it has to do with overactive sebaceous glands in the skin of newborn babies, due to the mother's hormones still in the baby's circulation. The glands release a greasy substance that makes old skin cells attach to the scalp instead of falling off as they dry. There is a relationship with skin yeasts (Pityrosporum ovale, newly renamed Malassezia furfur).
Cradle cap
Tram track 
Tycoon's cap
Cramp-ring
Oak wilt
Half and half nail
Crown 
Hair whorl