Probably one of the most common skin challenges and one of the most difficult to solve. The quicker you can tackle this issue the better. The older the brown spots the more Herculean it is to fade them and even the smallest amount of UV light can reactivate them. The objective is to squash melanin activity and put those pigmented cells to sleep. In lieu of immediately trying hydroquinone, which is quite controversial, try vitamin C, licorice extract, kojic acid or retinol. I like vitamin C in the AM and retain-A at night. Also exfoliate often, but gently with manual scrubs or exfoliating acids such as glycolic or salicylic. When utilized regularly exfoliant will lessen the appearance of dark spots by breaking the darker cells apart. A hint: take exfoliation easy during the summer when melanin cells are active, too much scrubbing and rubbing can actually trigger them.
Pigmentation is not only stimulated by sun and over-exfoliating but also by heat. Those prone to brown spots need to keep skin cool, especially post-exercise. Not only is keeping on plenty of sunscreen or simply staying out of the sun, possibly hot yoga is not such a "hot" choice.
Cheers, Miss Violet