According to the search results, there is no scientific evidence to suggest that Vaseline can darken lips. Vaseline is basically petroleum jelly, a type of occlusive moisturizer that helps lock the moisture in your skin. It works by forming a protective barrier on the lips to prevent moisture loss, which means that it does not add any moisture to your lips but seals in the existing moisture, making it an effective lip therapy product. Vaseline is good for lips, and it is a safe and gentle way to retain moisture in your lips and keep them protected. It strengthens the skin barrier and helps deal with extreme dryness and irritation. Vaseline lip therapy products are made with triple-purified petroleum jelly, which helps repair dry, chapped lips and relieves discomfort by locking in moisture. They provide long-lasting moisturization to dry, dull, and cracked lips. Vaseline lip therapy products are also clinically proven to help heal dry lips. Therefore, Vaseline is a good product for lip care and does not darken lips.