I used johnsons baby lotion on my 5 week old baby. he developed acne on face. not sure i its heat rash or acne. how to check and what's the treatment.

Doubt acne.: Babies don't have the hormones needed to cause acne. And 5 weeks is too old to still have maternal hormones. Allergy or irritation to some component of the lotion is a possibility. Stop the lotion. If the rash doesn't go away promptly, you'll need to check with your doctor.

Your PCP/Peds : Babies often get a transient "baby acne" that is not present at birth (bathed in the waters of the womb) but comes out at a few weeks & lasts a few months.It is thought to result from maternal hormone effect which gradually declines as the baby ages.It will generally disappear without specific treatment.I avoid lotions for babies.I think it aggravates their acne and leads to more bathing & dry skn.

Avoid lotion face: I would advise avoiding johnsons baby lotion on the face. It is not needed. Baby acne is secondary to hormonal changes and usually resolves spontaneously.