The reason for the appearance of hard bumps on the arms is a relatively common phenomenon in clinical daily life, there are many reasons for the bumps on the arms, the most common reasons are the following: 1, papular urticaria, after the mosquito bite, the skin on the arms will appear localized redness, swelling, plaques, plus repeated scratching to stimulate the arms will appear hard bumps, can be treated with topical glucocorticoid cream. 2, lipoma, if the arms appear 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.