Hydroquinone

Hydroquinone is an active ingredient with skin-lightening properties and is used in over-the-counter topical products to correct skin discoloration associated with hyperpigmentation disorders (e.g., sun spots, freckles, melasma). It is often used in combination with alpha-hydroxy acids, corticosteroids, retinoids or sunscreens.

Dihydroxybenzene was discovered in 1844 during a dry distillation. Due to several complications during use, such as skin irritation, exogenous discoloration and carcinogenicity, hydroquinone has been banned in cosmetic products in the EU and the UK.

Pharmacodynamics

By inhibiting the enzyme tyrosinase, which is involved in the initial step of the melanin pigment biosynthesis pathway, melanin production is downregulated and the skin is depigmented (decolorized). This lightening of the skin is reversible and can be recolored by sunlight.

Pharmacokinetics

Hydroquinone is excreted mainly in the urine.

Contraindications

The drug should not be used in case of:

• Hypersensitivity
• Non-melanin pigmentation
• Vitiligo (white spot disease)
• Skin cancer
• Acute dermatitis and eczema
• Bacterial infections
• During pregnancy and lactation
• Children under 12 years of age

Side effects

Common unwanted side effects include:

• Dry skin
• Allergic skin reactions (redness, (contact) dermatitis)
• Blue or black discoloration of the skin
• Increased body hair
• Thinning of the skin
• Steroid acne
• Stretch marks

Toxicological data

As a result of overdose, symptoms may include vomiting, dizziness, shortness of breath, mental confusion, and circulatory shock.