Skin Spots Darkening After Hydroquinone

Skin can darken in response to hydroquinone, but it takes some time using it (for most around a year or so) to develop this darkening, called exogenous ochronosis.

Two applications are not sufficient.  However, both the hydroquinone and the retinoid can be irritating to the skin, and the irritated area can be darker than the rest of the skin.  The irritation can be just because the ingredients are too strong or are applied too often or because you are allergic to one or more of the ingredients.

Again, a contact allergy takes time to develop.  For a first time user of these ingredients, it generally takes from 3 to 10 days of use to develop an allergy.  So most likely it is an irritation that is causing the darkening of the skin.

I recommend stopping the creams for 1-2 weeks and using a thin layer of a hydrocortisone cream twice a day for 3 days.  Make sure you are not applying the hydrocortisone cream anywhere around the eyes.  The irritated area should lighten.  If it does not, see your dermatologist for further care.

If this is an irritation, you can try to restart the fading cream on a small area at twice a week regimen and slowly increase the use to every night as your skin allows.  If the hyperpigmentation recurs when you resume the cream, don't use it anymore.

I would suspect an apparent darkening for a few reasons.  If you look at the color of skin, it is composed of the interplay of four pigments:  melanin (brown pigment in cells), oxyhemoglobin (red), deoxyhemoglobin (blue), and collagen (yellow).  Application of retinoic acids and hydroquinone can cause infammation which will increase blood flow to the area and an paradoxical darkening of the lesions.  As a mainstay of therapy, hydroquinone still has the down side of irritation.