Some plants contain chemicals which can sensitise the skin to sunlight. If an individual comes in contact with such a plant and simultaneously gets exposed to sunlight, he is likely to develop hyperpigmentation in the areas exposed to the plant and the sunlight.
As a rule, there are no signs of inflammation, but occasionally the patient may develop blisters as well. A similar picture can also be produced if the patient gets exposed to perfumes used as such or present in cosmetics, or similar compounds present in the purified extracts of plants, and oils used for hair or skin.
The lesions are primarily located on the areas not covered by clothes. The exact distribution will therefore depend upon the style of clothing that the person wears. The shapes and the sizes of these macules will depend upon the causative agent.
If the patient is exposed directly to the leaves of the plant as during lying down on grassy plots along the swimming pools or sea-beaches, the pattern of pigmentation may resemble the shapes of the leaves of that plant.
If the exposure is to the perfumes, the lesions may occur as minute punctuate spots if the perfume was used as a spray, or as irregular smudges if the perfume is applied with the hand or cotton balls. Linear streaks with a drop like appearance may be produced if the perfume flows down from the area of application (Berloque dermatitis).
In case the cause is a perfume present in a cosmetic, the pattern of the lesions will correspond to the areas where the cosmetic is applied.
In case a hair oil is responsible, the pigmentation is more around the forehead, ears, sides of the face and the upper central part of the back not covered by the blouse. The common habit of having oil baths among the residents of Tamil Nadu, Andhra Pradesh, Karnataka and Kerala has often produced irregularly shaped and ill defined smudges of pigmentation on the forehead and cheeks of these individuals.
In all these conditions, it is important to find out the causative agent and advise the patient to prevent further exposures to the same as well other similar agents. In case there is no clue to the causative agent, further exposures to all kinds of plants/perfumes must be stopped and the skin protected from sunlight. These measures should be able to prevent the appearance of new lesions.
The old lesions tend to disappear by themselves in due course, but the time taken for this, depends upon the intensity of hyperpigmentation and may take several months.
This can, however, be hastened by the local use of hydroquinone which should be massaged into the lesions once or twice a day. Vitamin C may also be given in doses of 5 gm a day as described for chloasma.