This mail be eczema. Please send photos using online consult option for proper examination diagnosis and treatment advice

The cause for the pigmentation needs to be determined. Smoking is one of the common causes for darkened lips. Stop smoking if you smoke. There are multiple other causes for hyperpigmentation also. Sun tan, overweight, pigmentation disorders like acanthosis nigricans or melasma, lichen planus pigmentosus, rhiel's melasnosis, nutritional deficiency etc are some conditions. The patches of pigmentation need to be examined and assessed to know the causeAlso you can use Chaptex lip balm twice a day for a few months. Hope this was helpful.