The causes of recurring hardened pimples on the chin may be acne, epidermoid cysts, folliculitis, and so on. 1. Acne: Acne is mostly related to androgen-induced increase in sebum secretion and abnormal keratinization of hair follicles, which may cause local inflammatory papules, pustules, nodules and other symptoms, and so may lead to recurrent hard pimples on the chin. 2. Epidermoid cysts: Because the chin secretes more oil, if you can’t pay attention to chin cleaning, the follicle holes will be blocked, resulting in a large amount of oil discharged poorly. Excess oil will accumulate in the hair follicle for a long time, leading to local skin fibrous connective tissue proliferation, and then form cysts. And there will be more necrotic tissue and grease in the cyst, which is a hard bag when you touch it. 3. Folliculitis: there are a lot of sebaceous glands and skin follicles in the chin, leading to excessive oil secretion in the area, which is easy to provide favorable conditions for bacterial reproduction, so that bacterial infection of the hair follicles, which induces folliculitis, appearing repeatedly in the case of growing a hard bag of pimples. If you are a patient with recurring pimples, it is recommended that you go to the hospital as soon as possible to identify the specific cause of the disease, and under the guidance of the doctor to treat the symptoms, so as not to delay the condition.