Rash with white tips is usually a manifestation of pimples. Rash with white tips on the arm may be caused by eczema, keratosis pilaris, boils, etc., and should be promptly consulted to find out the cause of the disease. 1. Eczema: inflammation of the superficial dermis and epidermis caused by a variety of internal and external factors, occurring in the face, hands, forearms and other exposed parts of the face, often manifested as erythema on the basis of the pinhead to corn size papules, papules, severe blisters can appear, may be accompanied by itchy symptoms. 2. Keratosis pilaris: mostly related to heredity, metabolic disorders, vitamin A deficiency, etc. It is often manifested as follicular keratotic papules on the upper limbs, extensor sides of the lower limbs, buttocks and face, with yellowish-white keratinous plugs in the center of the papules. 3. Boil: due to the invasion of staphylococcus aureus and other pathogenic bacteria in the hair follicles and surrounding tissues, resulting in acute suppurative lesions of the hair follicles, at first the local area can appear gradually enlarged red nodules, conical elevation, the top of the pus can be yellowish-white head. When a large red rash with white tips appears on the surface of the skin, you should consult a doctor in time to clarify the cause of the disease, and if necessary, carry out appropriate treatment.