1. Blackheads are the primary lesion of acne. They are cheese-like, semi-solid plugs clogging the sebaceous follicle opening. The exposed tip darkens at the follicle's surface. When squeezed, a black-headed, yellowish-white, translucent sebum plug emerges.
2. The primary lesions are inflammatory papules, ranging from millet seed to pea-sized, firm bumps appearing pale to deep red. The center of the papule may contain a blackhead or a sebaceous plug with an unblackened tip.
3. Lesions appear as millet-to-broad bean-sized bluish-red or purplish-red papules, pustules, or nodules. They are soft to the touch and contain pus and blood. These lesions persist for extended periods before healing, leaving behind minute scars. They are painless and show minimal infiltration. This type is commonly seen in patients with weakened constitutions.