Why doesn't hydroquinone work for all cases of melasma?

Skin discoloration is a very prevalent problem in women over the age of twenty.  It is also increasingly common in men with increased sun exposure, but mainly occurs in women. 
Risk factors include thyroid disease, sun exposure, hormones, pregnancy, family history, PIH, and birth control. Melarase AM and Melarase PM have been extremely effective in reducing pigmentation associated with skin discoloration and hyperstimulation of melanocytes. 
In my practice, patients with hyperpigmentation benefit from twice daily application of the creams. Melarase AM in the morning, followed by Melarase PM in the evening. Melarase AM contains four active sunblocks, so additional sunscreen is not needed unless your sun exposure is very high or you had a recent procedure/laser. SPF of 30. Melarase PM contains active skin lighteners to even out skin pigmentation. If you are concerned about the development of pigmentation, contact our office to discuss details and to obtain a regimen for Melarase. 
Laser therapy works but must be combined with a therapeutic topical program before and after therapy. 
Recommendations:  5-step Daily Brightening Kit has everything you need to improve dark spots, skin discoloration, melasma, and hyperpigmentation caused by sun exposure, hormones, scarring, and the environment. It’s a powerful daily brightening kit that can help bring out your skin’s natural, healthy glow. Ideal for use on the face, neck, and hands. 
Includes: Melaclenz, Melapads, Melarase AM, Melarase PM, Elevase, and Spectrase
Best, 
Dr. Karamanoukian
#Realself100 Surgeon

Melasma often needs combination treatment and I find that topical hydroquinone is only helpful in a few number of patients, very few.  Lasers, peels, microneedling/PRP along with skin care is the only way to improve melasma.  Remember there is no cure however and you will need long term maintenance.  Best, Dr. Emer.

There is a lack of penetration to deeper areas limiting effect. A different approach which is effective in any color of skin is the vi peel which in one week will improve melasma .Thre is no downtime and the peel can be repeated if necessary in a few months with a booster version.