Post-inflammatory hyperpigmentation is a common pigmentary skin disorder that is refractory to treatment. The treatment for postinflammatory hyperpigmentation is limited. Recent studies have shown that the topical skin care product cysteamine cream has a significant decrease in melanin index without obvious side effects in other dark spots such as melasma. The goal of this study is to determine the safety and efficacy of topical cysteamine in the treatment of post-inflammatory hyperpigmentation.

Post-inflammatory hyperpigmentation is a common pigmentary skin disorder that is refractory to treatment and troublesome for darker skin individuals. The current treatment with conventional bleaching cream may result in skin irritation and ochronosis that is irreversible. Recent studies have shown that the topical cysteamine cream is safe and effective for dark spots such as melasma and lentigo with no significant side effects.

The primary aim of this study is to evaluate the safety and efficacy of topical cysteamine for postinflammatory hyperpigmentation. We conduct a randomized control, double-blinded trial to include 40 patients with postinflammatory hyperpigmentation. Clinical photography with VISIA skin imaging system,mexameter, transepidermal water loss, optical coherence tomography were used to evaluate the efficacy of treatment on a monthly basis for four months period. The patient was evaluated by two blinded investigator using the investigator global assessment. Patient global assessment was also recorded monthly.

Inclusion Criteria:

• Over 20 years old
• Patients with postinflammatory hyperpigmentation for more than 3 months.

Exclusion Criteria:

• Patients with topical hydroquinone, oral tranexamic acid and/or other skin whitening agents.
• Patients that receive or planning to receive laser treatment for spot removal during the study period.
• Individuals with allergic history to cysteamine or vehicle ingredients.
• Pregnant patients or patients planning to become pregnant during the time of the study.

The packaging and labeling of the topical product were the same in both group. The subjects were randomized in by an interactive web response system that provided study kit number from the randomization list at the time of inclusion into the study. The randomization list was kept strictly confidential throughout the study and was not available to the investigator and patient or any other personnel who may influence the study data.