Melasma is caused by excessive or uneven distribution of pigment melanin in the skin but the reason why this is happening is unknown and that is why it is not possible to address the cause - you can only treat the symptoms. Sun protection is crucial because pigment producing cells (melanocytes) produce melanin upon sun exposure (melanin is our natural UV filter).
I have not recommended applying zinc based creams immediately after dermarolling because zinc oxide has astringent (contracting biological tissue) effects and it dries out the skin. The skin should be kept moisturized right after dermarolling. However, it is very important to protect the dermarolled skin from the sun so if you have to go outside immediately after microneedling, moisturize the skin (preferably with for example almond oil and apply sun protection on top of it. You can apply zinc-based cream a day after dermaneedling but it would be still wise to apply a little oil first.
In your case, I recommend buying a 0.5 mm dermastamp (not a dermaroller) and using it three times a week to enhance skin lightening product (such as hydroquinone) to the affected area. Do it for three months and then a one month break and so on.
In 2011, there has been a study about enhancing the penetration of skin depigmenting products by dermaneedling with successful results: Skin Needling to Enhance Depigmenting Serum Penetration in the Treatment of MelasmaG. Fabbrocini, 1 ,* V. De Vita, 1 N. Fardella, 1 F. Pastore, 1 M. C. Annunziata, 1 M. C. Mauriello, 1 A. Monfrecola, 1 and N. Cameli2
Copyright © 2011 G. Fabbrocini et al.AbstractMelasma is a common hypermelanotic disorder affecting the facial area which has a considerable psychological impact on the patient. Managing melasma is a difficult challenge that requires long-term treatment with a number of topical agents, such as rucinol and sophora-alpha. Aims. We aim to compare the combined treatment of skin needling and depigmenting serum with that using depigmenting serum alone in the treatment of melasma, in order to evaluate the use of microneedles as a means to enhance the drug's transdermal penetration. Methods. Twenty patients were treated with combined skin needling and depigmenting serum on one side of the face and with depigmenting serum alone on the other side. The outcome was evaluated periodically for up to two months using the Melasma Area Severity Index score and the Spectrocolorimeter X-Rite 968. Results. The side with combined treatment (skin needling + depigmenting serum) presented a statistically significant reduction in MASI score and luminosity index (L) levels compared to the side treated with depigmenting serum alone, and clinical symptoms were significantly improved. Conclusions. Our study suggests the potential use of combining skin needling with rucinol and sophora-alpha compounds to achieve better results in melasma treatment compared to rucinol and sophora-alpha alone.
You may also be interested to read this:Successful treatment of hydroquinone-resistant melasma using topical methimazolehttp://onlinelibrary.wiley.com/doi/10.1111/j.1529-8019.2012.01540.x/pdf