Most of the time dark spots or brown spots left after trauma or a burn to the skin are not permanent, although sometimes they can last a long time.

Dark spots (post inflammatory hyperpigmentation) on the face after acne

How long they last depends on a number of factors:

• how much pigment there is in the skin initially. Post-inflammatory hyperpigmentation tends to be worse and last longer in skin types IV-VI that have higher amounts of melanin.

• how deep the injury is. Deeper injuries that go into the reticular dermis cause scars (changes in skin texture) and leave long-lasting pigmentary changes lighter or darker than normal skin tone. If there is a burn that does not cause a blister or break in the skin, it has not reached the reticular dermis. To cause a blister, the injury should have reached at least to the junction between the top two layers of the skin (epidermis and dermis).
• how much ultraviolet light gets to the skin after the injury. UV light either from the sun or tanning equipment can worsen the hyperpigmentation and make it last significantly longer.

There are many popular home remedies found on the internet, such as petroleum jelly, lemon juice, aloe, tomato paste, among others. I would not advise using any of these methods as they all can cause additional inflammation and darkening of the skin. Using petroleum jelly (Vaseline) can lead to acne breakouts on the face, which will compound the problem.

The most important thing one can do after hyperpigmentation has already occurred is to use a broad-spectrum, oil-free non-comedogenic sunscreen with a high SPF to protect the injured areas from sun exposure.

Additionally, there are a number of topical medications that can improve the hyperpigmentation. If the injury is recent, I would just use sunscreen and give it 2-3 weeks to see if there is improvement.

If there is still inflammation and redness around the injured area, I would discuss using an anti-inflammatory topical such as a cortisone (not around the eyes) for a few days with your dermatologist.

If there is no inflammation and no improvement after 2-3 weeks, products like topical hydroquinones alone or in combination with retinoids (relatives of vitamin A) and cortisones can be tried to improve the pigmentation. Care must be taken with hydroquinones as longer use of these products can cause paradoxical hyperpigmentation.

I must add that without seeing the patient and the extent of the injury it is impossible to give correct medical advice and I am attempting to give general guidelines here. I would recommend a consultation with a board-certified dermatologist for a more definitive diagnosis and treatment.

More information on treatment of dark spots (hyperpigmentation) http://www.advancedskinwisdom.com/melasma.htm