Change your toothpaste. Fluorine containing toothpaste can cause such rashes. Don't use any cosmetic product on lips or around lips. If you are using general lightening Cream, stop using it. Have good diet, with fresh fruits, green veg, daal. Avoid repeated smacking of lips if you are used to it. Get you Vit
B12 level checked. Use moisturizing lip balm with SPF 15