Hard lumps under the skin may be related to lipoma, subcutaneous nodules, enlarged lymph nodes, acne and other diseases. 1. Lipoma: located in the subcutaneous, preferred in obese patients, seen in limbs, chest and abdomen, located in the subcutaneous or deep tissue, painless round nodules. 2. Subcutaneous nodules: preferred in elbows, ankles and other parts of the body, located in the subcutaneous with round or oval substantial hard lumps. 3. Enlarged lymph nodes: preferred in the area behind the ear, armpit, around the clavicle, etc., with single or multiple hard lumps, some of which may be movable or immovable, painless or painful and other discomforts. 4. Powdery mildew: it occurs in the oily skin people, common parts in the head and face, neck and chest and back, the surface is smooth, if there is a combination of infection, there will be pus, usually manifested as local redness, swelling, pain and so on. There are many other causes of hard lumps under the skin, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor to determine the treatment program, to avoid blindly using their own medication.