Pimples are a common skin condition for people of all ages. While pimples on the face, back, neck, chest, and shoulders are more common, pimples can occur on the arms as well.If you find red bumps or pustules on your arm, there’s a good chance that you have a typical pimple on your arm. However, it could be an indication of a more serious underlying condition.What’s a pimple? – A pimple, a symptom of acne, is caused by the opening of a pore. This allows bacteria, dead skin, or oil to enter the pore, which can then trigger a response from your body. Your body begins to fight the foreign substances in your pore, and that’s what causes a red bump to form. Sometimes the red bump will form a pus-filled head.Common causes of pimples include: Tight clothing. Sweat can clog your pores and cause pimples to pop up. If you’re wearing tight clothing, your sweat has nowhere to go; avoid wearing tight clothing if possible. If you must wear tight clothing, be sure to remove the clothing and wash your body when you’ve finished your activity. Hormonal change or imbalance. During puberty, a teen’s body is going through many hormonal changes. An increase in hormones can cause the body to create more natural body oils. These oils contribute to creating pimples or acne. Hygiene. If you aren’t following a proper skin care routine, you may find more pimples are making an appearance. When you wash your body, you’re removing dead skin cells and oil. If you aren’t washing your body frequently enough, the dead skin can build up and cause more pimples. Skin products. While good hygiene is important, some skin care products can cause pimples to occur. If you’re using a product that clogs your pores, you’ll notice an increase in skin issues.