Very few instances of contact allergic reactions to anthralin have been reported. However, transient primary irritation of uninvolved skin surrounding the treated lesions is more frequently seen and may occasionally be severe. Application of Dritho-Scalp must be restricted to the psoriatic lesions. If the initial treatment produces excessive soreness or if the lesions spread, reduce frequency of application and, in extreme cases, discontinue use and consult physician. Some temporary discoloration of hair and fingernails may arise during the period of treatment but should be minimized by careful application. Dritho-Scalp may stain skin, hair or fabrics. Staining of fabrics may be permanent, so contact should be avoided.