Caladryl Lotion may help soothe itching and irritation caused by minor skin allergies, rashes, insect bites, or prickly heat. However, for a 2-and-a-half-year-old child, it is best to consult a paediatrician before applying it, especially when the rash is on the buttocks. The skin in this region can be sensitive, and the cause of the rash may not always be an allergy. It could be due to diaper rash, fungal infection, irritation, or another skin condition that may need different treatment. If your doctor advises using Caladryl Lotion, apply only a thin layer to the affected area as directed. Avoid applying it to broken skin, near the genitals, or on large areas of the body. Seek medical advice if the rash spreads, becomes painful, develops swelling or discharge, or does not improve within a few days.