Post Inflammatory Hyperpigmentation (PIH)
- Post inflammatory hyperpigmentation (PIH) is the dark discoloration that follows an inflammatory wound.
- People with skin of color are prone to post inflammatory hyperpigmentation, especially after acne.
- PIH is sometimes even more traumatic and psychologically distressing than the original acne.
- PIH is difficult to treat but can be manages with topical agents and in office procedures
- Over-the-counter products are usually not strong enough to greatly improve PIH.
- Exposure to UV radiation from the sun will make dark spots from post inflammatory hyperpigmentation worse and prolong the time it takes for them to go away.
Melanin production is the driving force behind post inflammatory hyperpigmentation. Hyperpigmentation from trauma occurs when melanocytes (the skin cells that make a pigment) get irritated by the inflammatory response and create too much payment. This pigment gets trapped in the top layers of dead skin cells and/or the deeper layer called the dermis.
Any inflammatory process caused by a rash or trauma can result in hyper pigmentation. Post inflammatory hyperpigmentation is more common in people of color with darker skin types.
When a rash or inflammatory response clears it will often leave behind a dark spot or patch in the same location and pattern that the rash originally presented. Thus, post inflammatory hyperpigmentation can look like small dark flat spots when it results from acne or large irregular patches if it follows the pattern of a burn or eczema flare.
Post inflammatory hyperpigmentation will often resolve on its own as long as the process that led to the pigmentation does not continue. The process of natural regression can take weeks to months. Fortunately, we have many topical therapies that help improve PIH and expedite this process. However, it’s important to note that the UV radiation from the sun can make PIH areas darker thus prolongs the time it takes for them to resolve.
The topical treatments used to treat PIH work by either promoting the exfoliation of the skin cells where the pigment is trapped or specifically targeting the melanocytes to decrease the overproduction of melanin. However, first line treatment is always sun protection and sun avoidance. The reality is, one should not even bother investing time, effort or money into seeking treatment if they are not committed to adequate sun protection. Once a commitment to sun protection is made, the next step is starting with a topical skin lightening agent that decrease the production of melanin and/or exfoliate the skin cells where excess pigment is trapped. There are various over-the-counter formulations and addition to prescription agents that are effective in treating PIH. Given the stubborn nature of this disorder, it is also common for people to combine topical creams with office procedures such as laser therapy or chemical peels.
Patients with hyperpigmentation should minimize sun exposure by reserving outdoor activities for before 10 AM or after 4 PM when the sun rays are less strong, use a broad-spectrum sunscreen during the day (and reapplying every three hours), wear wide brimmed hats, sunglasses, umbrellas, and protective clothing went outdoors. Sunscreen should be at least an SPF 30 and preferably a mineral-based sunblock with titanium dioxide and/or zinc oxide as an active ingredient.
First-line therapies (topical agents)
- Retinoids: even though retinoids are most commonly used to treat acne, they also help improve hyperpigmentation. This is because as the retinoids help the skin cells shed more rapidly the excess pigment that is trapped in those skin cells gets shed as well. Topical retinoids are very effective for both clearing acne and treating the PIH left behind. It’s important to remember that right now it’s can cause dryness and irritation to the skin if used to much or too frequently. Start using just one pea-size amount once a week and slowly advance from there. Examples of over-the-counter retinoids include retinol and adapalene. Prescription strength retinoids include tretinoin, tazarotene, and trifarotene.
- Hydroquinone: is a potent depigmenting agent that inhibits tyrosinase is which is an enzyme that controls the rate limiting step of pigment production in the melanocyte. Hydroquinone is considered the gold standard in hyperpigmentation treatment either as a monotherapy or combination therapy. While it is a very effective and safe topical treatment, it’s overuse can lead to a condition called exogenous ochronosis which is a reflexive permanent darkening of the skin. Thus, it’s important to use it for short periods of time (typically three-month intervals) and then give your skin a break for a few months by switching to a non-hydroquinone based lightening agent for maintenance. Hydroquinone is available through prescription.
- Cysteamine: is the newest agent on the market for combating hyperpigmentation. Cysteamine is a potent antioxidant that inhibits the tyrosinosis enzyme and other pathways in melanin synthesis. Numerous studies have shown it to be just as effective as hydroquinone however it does not carry the same risks of exogenous ochronosis which makes ideal for long-term maintenance therapy. Cysteamine is the active ingredient in the topical cream Cyspera. Cyspera is considered a medical grade over the counter product so it’s only available to purchase at a physician’s office or online through their RegimenPro account.
- Other topical agents used for the treatment of melasma include azelaic acid, kojic acid, ascorbic acid, arbutin/deoxyarbutin, licorice extract, and soy. These agents have varying degrees of effectiveness and have not been generally found to be superior to hydroquinone; however, they are useful alternatives when hydroquinone is not available or not tolerated.
- Chemical peels: are beneficial in the treatment of PIH and are considered a second line therapy when used as an urgent treatment. There are many chemical peeling agents and they are often used in different combinations and different strengths. These include glycolic acid, salicylic acid, trichloroacetic acid, mandelic acid, lactic acid. Things such as vitamin C, retinoic acid, resorcinol, and hydroquinone are often added to boost the skin lightening effect of a chemical peel. Depending on the peeling agent and its strength, chemical peels can be either superficial, medium, or deep. Because irritation from chemical peels can result in post inflammatory hyperpigmentation, these pills should be used cautiously, particularly in patients with darker skin types. Chemical peels our office-based procedures and not safe to perform at home. Dust is important to discuss chemical peels is an option with your dermatologist in person to determine which agent is best for your skin and your condition.
- Lasers and microdermabrsion are considered second- or third-line therapies for PIH and are typically considered in more resistant cases. The use of fractional laser therapy has shown promising results and is currently the only US food and drug in ministration approved laser treatment for melasma. The risk of post inflammatory hyperpigmentation is greatest in darker skinned individuals; laser should be used with extreme caution in these patients and spot test should be performed to determine an individual’s response to treatment.