There are a variety of reasons why a dermatologist will prescribe lightening agents. They may be used to reduce the appearance of age spots (sun spots) and hyperpigmentation or to reduce the appearance of skin conditions like melasma and vitiligo. Skin depigmentation/skin lightening agents are not all made the same.  Hydroquinone and monobenzone are often the chemicals compared when assessing prescription skin lightening ingredients. These medications work very differently however and are not used for the same indications.

Melanocytes

The production of melanin functions as protection for the skin from UV radiation and its harmful effects. Skin conditions that affect melanin tend to result in visible changes to skin pigmentation. Melasma is one condition that typically flares up after sun exposure and results in symmetrical patches of hyperpigmentation on the face. Exposure to UV radiation is also the main cause of environmental aging of the skin that leads to sun spots, wrinkles, and pigmentation changes.

Monobenzone

Monobenzyl ether of hydroquinone (MBEH), also called monobenzone, was first discovered to be a lightening agent because it was added to reduce the deterioration of rubber in the 1930s. Tannery workers started using the rubber gloves treated with this chemical as an antioxidant. After they wore them for some time they started to develop pigmentation changes similar to what is seen with vitiligo. After a prolonged exposure to the gloves on a regular basis the pigmentation changes would start showing up in other areas of the skin that did not touch the gloves. This indicated that a systemic reaction was occurring. After analyzing the gloves, it was found that by removing the MBEH the pigmentation changes stopped occurring. This resulted in the discovery of MBEH as an agent for depigmentation in patients with vitiligo.

Monobenzone is specifically for use in patients with vitiligo for who repigmentation is highly unlikely to be successful. The depigmentation that occurs after monobenzone use is permanent. In general, monobenzone is not recommended for use in younger patients for who repigmentation may be possible. There is always the possibility that in a few years a new treatment becomes available that can allow for repigmentation. If that is the patient’s preference, it may be worth waiting until they are older to proceed with full depigmentation.

Tretinoin is sometimes combined with monobenzone to enhance its effectiveness. When combined, tretinoin may reduce the amount of monobenzone required to achieve results.  Some patients with vitiligo may be resistant to treatment with MBEH. For these patients in particular, the use of topical tretinoin may improve results. Retinoic acid inhibits protective processes of melanocytes to allow the MBEH to work more effectively.

For most patients, the lightening process occurs over a period of 4 months to a year however treatments may continue for years after that to achieve complete depigmentation.

Hydroquinone

Hydroquinone provides skin lightening that may be considered more reversible than the depigmentation that occurs with MEBH. Hydroquinone is the gold standard for skin lightening when the concern is sun spots, hyperpigmentation, acne scars, melasma, and more. Various strengths can be made by a compounding pharmacy depending on the severity of the condition. Hydroquinone treatment is reversible in most cases, although in patients with certain skin types there can be permanent discoloration. Sun protection is essential as exposure to UV radiation can reverse the medication’s effects.

Monobenzone vs. Hydroquinone

One important difference between monobenzone and hydroquinone is that monobenzone results in a more permanent depigmentation and can cause a systemic lightening reaction. When monobenzone is used for a period of time it can cause depigmentation to occur in areas of the body distant from where it was applied. That means that if you are using monobenzone on your arm, you may then notice pigmentation changes on your face and neck.

Hydroquinone produces reversible inhibition of tyrosinase which reduces melanin production and selectively damages melanocytes and melanosomes. Monobenzone on the other hand is thought to destroy melanocytes more directly. MBEH has been shown to induce disintegration of the cellular membrane of melanocytes and release of cell contents which leads to their death. This difference is essential to understanding the difference between HQ and MEBH – one inhibits the production of melanin and the other destroys the cells that produce melanin.

It should be noted that monobenzone is not permanent in all cases. It is thought that it does not actually penetrate to follicular melanocytes – thereby not destroying all melanin producing cells and allowing for repigmentation.

What Treatment is Right for You

Your dermatologist is the one who can determine what lightening product is right for your skin condition. In general monobenzone use is limited to vitiligo and in studies for treating melanoma. Hydroquinone is the skin lightening ingredient used in most other cases.

Articles

Depigmentation therapies in vitiligo – Indian Journal of Dermatology

Monobenzone (Benzoquin) – FDA Package Insert

Monobenzyl Ether of Hydroquinone and 4-Tertiary Butyl Phenol Activate Markedly Different Physiological Responses in Melanocytes: Relevance to Skin Depigmentation – Journal of Investigative Dermatology

Retinoic acid synergistically enhances the melanocytotoxic and depigmenting effects of monobenzylether of hydroquinone in black guinea pig skin – Experimental Dermatology