My 18 month old son has a rash on the right side of his head/forehead. it's a little itchy to him but it doesn't hurt. i'm not sure what it is?

A localized rash on: one side of the head is most consistent with a contact allergic rash or dermatitis, especially if it is itchy. To confirm, a photo or exam is most helpful. Those usually clear in a week or so, but in the meantime, topical creams for itching, which can include hydrocortisone cream, may be helpful. A fungal infection,ringworm, is usually coin shaped, and impetigo is moist and crusty.