A lot of bumps like fat grains on the chest may be caused by folliculitis, acne, keloids and other reasons. 1. Folliculitis: due to the lack of attention to local skin hygiene, sebaceous glands secrete vigorously. It may lead to the blockage of the follicular opening, resulting in the propagation of bacteria and triggering folliculitis. So there are a lot of bumps like fat grains on the chest, sometimes itchy or painful. 2. Acne: Acne occurs when sebaceous glands secrete more oil and pores are blocked due to elevated androgen levels. It can be manifested as a lot of bumps like fat grains on the chest. 3. Keloid: Due to keloid or improper wound care and other reasons, the local scar tissue overgrows, causing keloid. So there are a lot of lumps like fat grains growing on the chest, and they are very hard to touch. There may also be other causes for many lumps like fat grains on the chest, so it is recommended to go to the hospital in time and ask the doctor to make a clear diagnosis and treatment.