Small blisters on the arm is very itchy consider herpes sweat or blistering tinea pedis, blistering eczema, etc., the treatment has a certain, need to carry out specific analysis. 1. Sweat herpes: sweat herpes caused by small blisters on the arm is very itchy, you can take oral antihistamines to relieve itching symptoms, such as loratadine tablets. You can also use topical tretinoin urea ointment and tacrolimus ointment to relieve and improve the symptoms. 2. Blistering tinea pedis: patients with blistering tinea pedis are mainly treated with topical medications such as ketoconazole cream, bifonazole cream, terbinafine hydrochloride cream, amorphophallus hydrochloride ointment, etc. If the effect of the topical medications is not satisfactory, the patients can use the topical medications to relieve the itching symptoms, such as clonidine tablets. If the effect of external drug treatment is not good, repeated episodes can be oral itraconazole capsules, terbinafine hydrochloride tablets, etc. for treatment. 3. Blistering eczema: If blistering eczema does not have many blisters and less exudation, zinc oxide ointment can be used for treatment. If there are more blisters, you can use boric acid solution to apply cold wet compresses locally after suctioning the blister fluid under the operation of a professional doctor. All of the above drugs should be used under the guidance of a doctor, it is recommended that patients seek medical attention to confirm the cause of the disease for targeted treatment.