Factors that can cause pigmentation;

1. Heredity ; dark-skinned individuals have a higher predisposition to hyper-pigmentation.
2. Hormonal ; Pregnancy can cause skin pigmentation particularly on the breast area & the midline of the abdomen. It can also cause pigmentation marks on the face known as chloasma or melasma. Some refer to it as pregnancy mask. It can disappear after the birth or after ceasing breastfeeding. Unfortunately sometimes it doesn't disappear at all.
3. The contraceptive pill ; This can cause pigmentation on the face, because of the high dose of oestrogen being taken. Some pills contain more oestrogen than others and are therefore more likely to contribute to pigmentation marks. e.g. Dianette has 4 times more oestrogen than most pills, so anybody taking it must be sure to wear a sunscreen to avoid this.( hormonal pigmentation usually occurs around the mouth and is the most difficult to treat.)
4. Addisons Disease ; which is related to the under secretion of the corticosteroid hormones from the adrenal glands, will have many symptoms including hyper pigmentation.
5. Stress ; Prolonged stress can over stimulate the adrenal corticoid hormones from the adrenal glands, secreting too much cortisone resulting in hyper- pigmentation
6. Post-inflammatory ; Any time the skin experiences infection (i.e. acne) or injury (i.e. burn with the iron) the skin will produce pigment leaving a brown mark at the site of the burn or where the acne spot was. In dark skin this is more severe and can result in a deeply pigmented area, which may disappear with the natural shedding of dead skin cells but often does not disappear at all.
7. Sun exposure ; Prolonged over exposure to the sun can over stimulates the production of melanin resulting in pigmentation marks. Anyone continuing with sunbathing or sunbed use will not respond positively to salon treatments to reduce pigmentation as it would be counter productive. Sunburn causes skin inflammation, which can also result in hyper pigmentation.
8. Photo Sensitivity ; Certain chemicalsand ingredientsfound in cosmetics and skin products will create a photosensitive reaction; these include Lime oil, bergamot, Retinoic Acid (Retin A), Renova, & fragrance. (To make one smell in a perfume it takes 1000 chemicals) Pigmentation is common on the neck where perfume is sprayed. Perfumed deodorants can cause underarm pigmentation.
9. Medications ; i.e. Accutane, Tetracycline, & diuretics, will also contribute to pigmentation. Anti cancer, hypoglycaemic & non steroidal anti-inflammatory drugs are all agents that contribute to photosensitivity
10. Ageing ; After the age 30-35 the number of pigment producing cells begin to decline making skin more prone to brown spots. From age 50 the pigment producing cells are reduced by 50% increasing the susceptibility to liver spots.
11. Skin diseases & disorders ; Some skin diseases & disorders, particularly if they cause inflammation or skin thickening can cause hyper pigmentation & hypo-pigmentation (lack of pigment) i.e. psoriasis, eczema, icthyosis, dermatitis
12. Trauma ; i.e. severe sunburn, cuts, wounds, burns, aggressive chemical peels (i.e. TCA Peels), surgery, post-operative reactions to anaesthesia, birth control pills, & HRT.
13. Drug-induced Hyper-pigmentation ; Some drugs contribute to pigmentation, i.e. anti biotics such as tetracycline. Amiodarone, minocycline, bleomycin, chlorophosphamide. Anti malaria drugs such as chloroquine & quinacrine. Acne drugs such as Retin A & Roaccutane can also trigger pigmentation marks. Using a physical sunscreen is imperative when using any of these drugs, to help avoid hyper-pigmentation.