The first step to preventing lentigines is good skin care and adequate protection from the sun and UV rays. The long-term and daily use of sunscreen has actually shown to reduce the chances of developing lentigines. Wearing wraparound sunglasses and a hat while outdoors will also offer additional protection from the sun.
Over-the-counter medications probably will not radically improve the lentigines, that said a variety of bleaching agents and exfoliates may help mild lesions these include hydroquinone, alpha-beta hydroxy acids, vitamin C, azelaic acid and retinoids. The most effective therapy is probably laser the chemical peels and liquid nitrogen cryotherapy are also commonly used.