There are several conditions to consider when you have bumps on your arms: 1. Keratosis pilaris, the disease is caused by autosomal dominant inheritance, and the rash manifests itself as follicle-consistent papules on the extensor side of the upper arm, with slightly conical papules and fine, soft hairs passing through the tip. 2. Eczema, caused by excessive consumption of spicy and irritating foods, such as raw onion, raw garlic, chili pepper, etc., or contact with allergy-prone plants such as lacquer trees, or contact with animal fur, such as cat hair and dog hair. Allergic reactions caused by animal fur, such as cat hair, dog hair, etc. 3. Contact dermatitis, an allergic condition that may be caused by local application of ointment, or application of safflower oil.