Foot lesions are abnormal patches of skin, according to Healthline. These areas may be primary or secondary lesions. Some skin lesions are caused by infections, others are hereditary, and still others are caused by medical conditions such as diabetes or an allergic reaction.
Primary skin lesions include blisters, macules and pustules, says Healthline. Macules are small spots on the skin, such as freckles and flat moles. Pustules are small lesions filled with pus; impetigo, acne and boils typically cause them. Allergic reactions cause primary lesions such as rashes and hives. Some primary skin lesions are present at birth, such as birthmarks.
Secondary lesions appear when primary lesions are aggravated or irritated in some way, explains Healthline. Scales, ulcers, scabs, atrophied skin and certain scars are examples of secondary lesions. Scales occur when patches of skin cells concentrate and then fall off, while ulcers are caused by infections and trauma. Dried blood on a scratched lesion creates a scab, or crust. Thin, atrophied skin lesions are caused by overuse of creams and topical steroids, and a laceration that does not heal with healthy, normal skin creates a lesion called a keloid scar.
Warts are skin lesions caused by an infection; other infections that cause lesions all over the body are chicken pox and shingles, notes Healthline. Moles and freckles are hereditary lesions. Diabetes and poor circulation may cause lesions due to sensitive skin. An autoimmune disease such as psoriasis causes chronic skin lesions.