Hello Dylan,masturbation doesn t lead to undereye dark circles.There are various factors attributed to the causation of undereye dark circles which include-genetic/familial factors,stress, post inflammatory hyperpigmentation, atopic or allergic contact dermatitis, anemia, stress, periorbital edema, superficial location of vasculature, and shadowing due to skin laxity, etc.Masturbation is not proven to be one of the cause.Treatment or correction of the underlying cause is extremely important.Topical modalities include- depigmenting agents like kojic acid, azelaic acid, topical retinoic acid,hydroquinone (to be careful in this sensitive areas).Therapies such as chemical peels, fillers for filling of the tear trough if present and laser therapy can also be tried along with topical treatment.These will lead to gradual lightening of the pigment with time.Hope this helps.Take care