The perioral region of the face seems especially sensitive to these changes. Unprotected exposure to sunlight can worsen the condition.
If you are getting lighter skin that shows signs of scaling or rash around your mouth, you might have perioral dermatitis which needs treatment from a physician. In this case you should avoid products with oils and heavy bases. Switching skin care products to oil-free foundations and oil-free moisturizers may help. Prescription medications such as topical or oral antibiotics can also be very helpful.