Small blisters on the back of his hand, eczema.

Small blisters on the back of your hand are most likely caused by an infection or allergy. If allergies are the cause, you can take oral anti-allergy drugs such as cetirizine or loratadine. If infections are the cause, you can choose terbinafine or econazole. Patients with severe itching can also use calamine lotion topically.