Will having a pus-filled sore on the calf be contagious to others?

Generally, ulcers on the lower leg caused by bacterial or viral infections may be contagious, while those resulting from non-infectious factors are not. If in doubt, it is recommended to seek medical advice in advance. Detailed analysis is as follows:

Ulcers caused by bacteria such as Staphylococcus aureus, streptococcus, or viruses like herpes simplex contain pathogens. Contact with broken skin may lead to transmission, thus posing a risk of infection.

If the ulcer is due to non-infectious factors such as local trauma, sebaceous gland blockage, or autoimmune issues, there are no pathogenic agents in the pus, and contact will not cause illness in others; therefore, this type is not contagious.

After the appearance of an ulcer on the lower leg, avoid direct contact with the affected area and secretions, wash hands frequently, and keep the area clean and dry. If the ulcer ruptures or symptoms worsen, seek medical attention promptly to prevent the spread of infection.