Caladryl lotion contains calamine and diphenhydramine, which is the active ingredient in the antihistamine Benadryl, according to WebMD. Caladryl and calamine are both over-the-counter preparations used to treat the itching associated with poison oak, ivy and sumac; bug bites; and minor skin conditions such as acne.
Calamine is also effective in drying up the oozing discharge that often accompanies poison oak, ivy and sumac, explains Mayo Clinic. It is available as a cream, lotion or ointment. To use the lotion properly, shake the bottle to mix the suspension, apply to a moistened cotton ball or gauze and wipe the lotion on the affected area. Ointments should cover the affected area, and then gently rubbed into the skin. Both formulas can be applied as often as needed for relief.
Caladryl is especially effective against itching because the diphenhydramine blocks histamine, a substance that causes itching in allergic reactions, states WebMD. It is safe to use according to package directions, though taking additional diphenhydramine should be avoided due to the potential for overdose. Oral antihistamines taken for allergies and colds often contain diphenhydramine. Discontinue use while using Caladryl.
Both Caladryl and calamine are designed for topical use only. They should not be used on mucous membranes nor used over large areas of the body, notes Mayo Clinic.