Ask a Dermatologist and a Chemist: How Does Hydroquinone Prevent Hyperpigmentation?

Our Chief Medical Officer, Dr. Courtney Rubin, and our Head of Chemistry, Lizzy Trelstad, weigh in on your most pressing skincare questions. 

What is hydroquinone?

Hydroquinone, typically found in skin discoloration treatment products, is known for skin brightening because it helps inhibit the conversion of tyrosine to melanin. What does this mean? It means that hydroquinone helps play defense against the formation of dark spots and hyperpigmentation in the skin.

Hydroquinone is unique because it’s incredibly effective at preventing the formation of dark spots and discoloration. Hydroquinone has been shown to decrease tyrosinase activity, the skin process that leads to hyperpigmentation.

How does hydroquinone work?

Very generally, hydroquinone can "trick" the tyrosinase enzyme (the enzyme responsible for triggering hyperpigmentation) into interacting with hydroquinone instead of its required substrates. The enzyme wants to continue on a multistep biochemical process toward the creation of melanin, but hydroquinone halts this process. Think of hydroquinone as a wrench that’s jammed in a converter belt. In this case, the conveyor belt is the process in which melanin is created. If the conveyor belt is jammed, melanin doesn't get made. 

Is this different from chemical exfoliation? 

Hydroquinone and chemical exfoliation (like AHAa) are very different skincare beasts, and shouldn't be tied together. Hydroquinone is for hyperpigmentation, and AHAs are for chemical exfoliation, which leads to smoother and more even-looking skin over time. If skin brightening and exfoliation happen concurrently over a period of time, using both processes, the skin will appear more even. But this result is not dependent on the use of both hydroquinone and chemical exfoliants.

Unlike the process by which hydroquinone halts hyperpigmentation, chemical exfoliation with AHAs does not involve enzyme disruption or redirection. Chemical exfoliation simply removes layers of dead, dull and uneven skin cells from the surface of the skin, revealing brighter skin underneath.

What is the number one cause of hyperpigmentation?

There are many causes of facial hyperpigmentation, the most common being post-inflammatory hyperpigmentation, which is pigment that’s left behind after an inflammatory condition resolves (for example, pigment left behind after acne or contact dermatitis). Other causes of facial hyperpigmentation include exposure to UV light, melasma, exposure to certain drugs or chemicals, exposure to photosensitizing agents, hormonal imbalances and dermatologic conditions such as lichen planus pigmentosus or erythema dyschromicum perstans. If you are suffering from new facial pigmentation, it's important to seek evaluation by a medical professional who can determine the underlying cause, which will help inform the best course of treatment.

How often should you be using hydroquinone per week if you hope to erase dark spots?

Dr. Courtney Rubin’s take:

The most important prevention and treatment for many types of facial hyperpigmentation is sunscreen! Sunscreen is the cornerstone of facial hyperpigmentation treatment, and I try to ensure all her patients are using sunscreen regularly before even talking to them about other skin lightening agents. I recommend an SPF 50 sunscreen that contains iron oxide pigments to block visible light in addition to UV light, as we know that visible light plays a role in pigmentary disorders like melasma. 

If people are already using sunscreen daily and want to try additional skin lightening agents, hydroquinone is an option. Hydroquinone is available over the counter in concentrations up to 2% and can be prescribed in higher strengths by a dermatologist. It's important to note that a rare but serious side effect of hydroquinone use is called exogenous ochronosis, which happens when hydroquinone is overused, and the treated skin develops a dark brown discoloration that is very difficult to reverse. Because hydroquinone can cause this serious side effect when overused, I usually recommend that patients use it as directed by a medical professional, who can follow the patient’s course and make sure the hydroquinone is being used correctly.