Small bumps on the arms are considered in the following cases: 1. Eczema, caused by allergic factors, may be due to allergy to sunlight and ultraviolet radiation, wearing long-sleeved clothes made of cashmere or chemical fibers and causing allergy. It may also be due to over-eating spicy and irritating foods or seafood such as shrimp, crab, scallops, beef and mutton, and other irritating foods that cause allergic reactions. The actual fact is that you can find a lot of people who are not able to get a good deal on a lot of things.