What happened to the child’s face when it suddenly developed a red bump and swelled up?

A child’s face suddenly long red bag is swollen, consider and eczema, contact dermatitis and so on.
1. eczema: children’s face suddenly appeared red bag, accompanied by swelling, may be due to eczema factors, the skin will appear pinhead to corn size pimples, severe localized swelling, like allergies.
2. Contact dermatitis: some children may belong to the allergic body, especially in contact with external allergens, will cause the body’s immune response, thus causing the above symptoms.
The child’s face suddenly long red bag is swollen, also does not exclude and mosquito bites and other factors, to determine the cause and then do standardized treatment, not blindly use drugs.