(ACD) is a form of contact dermatitis that is the manifestation of an allergic response caused by contact with a substance.
The most common causes of scalp allergic contact dermatitis (ACD) are with chemicals and fragrances ingredients found in hair dye, shampoos and conditioners
Paraphenylenediamine (PPD) is a chemical that is widely used as a permanent hair dye can cause extreme itching and rash. Pain can also be present.
The symptoms of allergic contact may persist for as long as one month before resolving completely. Once an individual has developed a skin reaction to a certain substance it is most likely that they will have it for the rest of their life, and the symptoms will reappear when in contact with the allergen.