Several conditions can cause lumps and bumps to form below the skin or on its surface, such as cherry angiomas, skin cysts, epidermoid cysts, keratosis pilaris and folliculitis, according to WebMD. Skin bumps can also result from infections, allergic reactions, hereditary diseases or acne, reports Healthline.
Skin bumps and blisters are common signs of a rash resulting from heat, eczema, hives or contact with poison ivy, reports MedicineNet. Psoriasis, an eruption of bumpy scales on the elbows, scalp or knees, is another noninfectious rash. Many patients also suffer from keloids, or hard, irregularly shaped scars. When skin is exposed to a substance that produces an irritant or allergic response, it can lead to a raised skin rash called contact dermatitis.
Skin cysts are pockets of tissue that are usually filled with fluid, according to WebMD. Patients say that cysts feel like peas under the skin's surface. Keratosis pilaris is a cosmetic skin disorder that usually appears as small bumps on the upper thighs, cheeks, arms or back. A cherry angioma is a smooth, red growth that normally does not require treatment. While these angiomas tend to grow on a patient's back, they can also occur everywhere else on the body.
Warts, insect bites, mollusca and corns are other common conditions that cause skin bumps, explains Healthline. Warts are rough bumps that are normally found on a patient's hands or feet.