A large pimple on the forehead with pain and hardness may be caused by boils, epidermal cysts, acne and so on, patients need to follow the doctor’s advice to choose the treatment of drugs. 1. Boils: Bacterial infections caused by lack of hygiene or excessive sweating lead to purulent inflammatory reactions in the deeper parts of the hair follicles and the surrounding tissues, resulting in large, painful and hard pimples on the forehead. You can apply mupirocin ointment, fusidic acid cream, 20% ichthyol ointment and other medications to treat it and play the role of anti-infection. 2. Epidermoid cysts: most of them are primary cysts, which can occur in any part of the body, and can be extruded as “tofu dregs”-like material, and will increase in size and redness and pain if secondary infection occurs. You can take amoxicillin capsule, cefixime capsule and other antibiotics to control the infection, and then do surgery to remove it after the infection is controlled. 3. Acne: caused by excessive sebum secretion and Propionibacterium acnes infection due to heredity and androgen, etc. Adapalene gel and benzoyl peroxide can be applied; patients with moderate-to-severe acne need to take oral antibiotics and isotretinoin for treatment. The causes of large, painful and hard pimples on the forehead are many, and patients need to go to the dermatology department of a regular hospital to get a clear picture of the cause of the problem and then under the guidance of the doctor for treatment.