Bumps on the top of the thumb may be caused by folliculitis, contact dermatitis, herpes sweat and other diseases. 1. Folliculitis: Bacterial infection, fungal infection, damage to hair follicles, decreased body immunity and other factors may trigger folliculitis. Patients often appear in the hair follicle as the center of the papule, sometimes there may be white pustules on the top of the papule, may also be accompanied by itching, tenderness and other symptoms. If it appears on the hand, it may be manifested as a pimple on the top of the thumb. 2. Contact dermatitis: chronic dermatitis caused by skin contact with exogenous substances, such as animal toxins, peaks, caterpillars, plant roots and leaves, chemical substances and other stimuli. Patients may show erythema, mild edema, itching, swelling, etc. In severe cases, it may also show erosion, crusting, and tissue necrosis. It may cause the patient to have bumps on the top of the thumb. 3. Sweat herpes: caused by local allergies, contact with heavy metals, dermatophyte infection, emotional tension and other factors. It may cause the patient to have itching, blisters, tingling or burning sensation and other symptoms, and the symptoms of having bumps on the top of the thumb. Patients with bumps on the top of their thumbs are advised to go to a regular hospital and under the guidance of a doctor, undergo relevant examinations to clarify the cause of the disease.