I was told that HQ4% could cause skin cancer if we used it for long term. Thus, we can only use it for short term. Is this true? What is the best way and best period to use HQ4% with Retin-A? Can we use these two things the same time?
I Was Told HQ4% is Not Safe for Long Term Use, is That True?
Doctor Answers 3
Is hydroquinone 4% safe?
This product is still on the market and is wonderful treatment for hyperpigmentation. It works best when it is combined with Retin-A so absolutely they can be used together. The science behind the "safety" concerns is spotty at best and personally, I use the product and recommend it to my patients.
It hasn't been proven to cause skin cancer but you should be cautious
Hydroquinone's chemical structure is similar to benzene which is used as a chemical detergent and bleaching agent in detergents you buy at the grocery store. The chemical is harsh on the skin and can cause redness, irritation and itching in some patients. It works by blocking the production of melanin, but with long-term use can cause other adverse effects such as a "halo" effect around a dark spot that you treat or uncommonly darkening in an area that has been treated long-term. Since the chemical does decrease the melanin (pigment) stores in your skin it has been extrapolated that it increases your skin's susceptibility to UV rays and to skin damage. Hydroquinone is also often combined with Retin-A which works in a different way to inhibit melanin production and sensitizes your skin to the sun's rays. Thus, they work together and hydroquinone alone has little effect compared with in combination with retin-A.
Hydroquinone has been studied in mice and shown to be a carcinogen but it was given by mouth and not applied topically as we use it currently. The FDA is currently considering a ban on the product based on these study results. Unfortunately, no study will ever be allowed in humans to test the potential carcinogenic ability in humans. It would be unethical... so we may never have an answer to that question but I would be cautious with long term use based on what I have mentioned so far.
Long term hydroquinone usage
Hydroquinone 4% is a low dosage, and many people are on it for significant amounts of time (see the Obagi line of products). There were studies published several years ago that showed long term hydroquinone wasn't good for treating mice. People have extrapolated that to say humans can't use it long term either. That's the info behind it. I don't have issues with long term usage even in higher dosages like 8% and have seen nothing in my practice to indicate it's harmful in any way.