What causes scarlet fever? Most of them are lesions.

Scarlet fever is a contagious disease that seriously endangers people's health. The reason for this disease is mostly due to the patient having purulent lesions, toxic lesions or allergic lesions.

1. Purulent lesions

When pathogens invade the pharynx or other parts of the body, since the M protein of group A bacteria can resist the phagocytic effect of the body's leukocytes, a suppurative inflammatory reaction may occur locally, causing suppurative pharyngitis, tonsillitis, and complications of adjacent organs, such as otitis media, mastoiditis, cervical lymphadenitis, etc.; if the bacteria invade the blood circulation, sepsis may result.

2. Toxic lesions

When bacterial toxins are absorbed into human blood, they cause systemic poisoning symptoms such as fever. The scarlet fever toxin causes congestion and edema of the blood vessels in the skin and mucous membranes, as well as epithelial cell proliferation and leukocyte infiltration, which is most obvious around the hair follicles, resulting in a typical scarlet fever rash. When the rash subsides, epidermal cell necrosis causes peeling, and the oral mucosa also becomes congested or has punctate hemorrhages, forming an intramucosal rash.

3. The course of allergic lesions is 2 to 3 weeks. A small number of patients develop allergic pathological damage, mainly non-suppurative inflammation of the heart, kidneys, and synovial joints.

Scarlet fever can occur throughout the year, but it is more likely to occur in winter and spring. People are generally susceptible to group A β-hemolytic streptococci, and after infection, the human body can produce antibacterial immunity and anti-toxic immunity. The disease is more common in children, especially those aged 2-10 years old. Infants under 6 months old rarely suffer from this disease.