Allergy to Parthenium
Parthenium hysterophorus also known as carrot grass or gajar ghas is one of the most toxic weeds of non-crop land area. It is a tall growing, deep-rooted plant with height 3-4 feet at the fully flowered stage.
The weed bears terminal white coloured flowers. The flowers in turn bear numerous seeds, which get easily dispersed by wind or water.
As soon as the winter season is over, the weed starts appearing and continues to do so till October-November (peaking during July - August), causing allergic reactions in a lot many people – in extreme cases even severe asthma attacks.
What is the source of allergy?
The allergy is caused by direct as well as indirect contact with Parthenium pollen. It causes severe contact dermatitis in a lot of people, which often becomes chronic after prolonged exposure.
The source of the allergy are the strong sensitizing sesquiterpene lactones - parthenin, ambrosin and others, which are highly concentrated in the trichomes of the plant. During the onset of the dry season, the mature plants crumble to a fine dust, that is scattered by the wind and get dispersed throughout. Long term contact with this dust, especially for those living in the country side, is the source of the often fatal "airborne contact dermatitis.”
Why is parthenium weed a source of concern?
Parthenium is a toxic weed, which can spread throughout at abnormal rates and in unusual density. Factors aggravating this are –
- the absence of natural agents that restrict the spread of this weed.
- high productivity level of the weed
- efficient seed dispersal mechanism through wind and water
- wide adaptability to varying soil and agro-climatic conditions that have enabled this weed to invade environments associated with human activities.
What are the ill-effects of the parthenium weed?
Parthenium is known to cause diseases like asthma, allergy and skin disorders. Airborne pollen of parthenium may cause severe allergic rhinitis in some individuals.
Prolonged exposure (ranging from 3-12 months) to the weed is the largest source of airborne contact dermatitis. Almost every part of the plant except root is a cause of frightening reactions in humans, which is mostly over the sun exposed area of the skin. In extreme cases of the allergy, people have drawn out water to the extent of 1-1.5 litres from their skin.
Even dried dusty material of the plant, such as the trichomes on the leaves and stem are air-borne and may induce dermatitis in sensitive people who do not have direct exposure to the weed.
What are the symptoms of the allergy?
The symptoms start with itching and blister like eruptions on the eyelids, neck, face, elbows and back of the knees.
Some individuals are so allergic to parthenium, that they need hospitalisation during its peak growing season.
Other common symptoms include:
- Chest tightness
- Recurrent symptoms of fever
- Cough, sneezing, itching
- Nasal discharge
- Dyspnea that worsens with exposure to the allergen
- It has been observed that persons suffering from the ill effects of the weed can be cured temporarily if moved to a weed-free area.
- Doctors consider parthenium allergy as normal allergy and give general treatment consisting of nasal sprays, antihistamines, corticosteroids.
- In Ayurveda also, although there are many herbal combinations for specific allergies, but nothing very particular to Parthenium allergy.
- Mustard oil when applied externally before and after exposure provides great relief from skin irritation.
- Rubbing the leaves of the mahua tree on the affected part of the skin also provides relief from itching, irritation and burning sensation.
- A preventive measure to any type of allergy is the use of jaggery and turmeric paste, and is frequently recommended.
How to control the allergic impact of parthenium pollen?
One of the problems while coping with parthenium pollen allergy is how to escape from the stuff because it is impossible to create a pollen-free zone. Pollens of wind-pollinated plants are small and light, easily get carried far and wide; and easily get inhaled right into the lungs. However, some preventive measures include:
- Make sure your allergy is well under control by consulting a doctor before the start of the pollen season (February onwards). Adjust or change your preventive medication to suit the increased exposure you will have to pollen over the coming months.
- Try to avoid the airborne pollen by staying indoors and using air purifiers.
- If possible, try to stay indoors and close the doors and windows on windy and humid days.
- Be aware of the times of day that are worse for your allergy during the pollen season. Follow your medication plan rigorously as instructed by your doctor.
Immunotherapy (injections of very small amounts of pollen allergen over several years to desensitize) is an option for some people with pollen allergy; consult your doctor if possible in this case.