Photodermatitis is an allergic skin reaction mostly reactive to light, especially sunlight containing UV rays. It is a form of allergic contact dermatitis. The allergen on the skin is to be activated by light to start the allergic response due to sensitization. It usually starts with a skin rash but can lead to further complications like systemic problems if the exposure is continued. Photodermatitis is termed especially when the skin rash due to light exposure is eczematous in nature.
Signs & symptoms
Reddish to black skin discolouration
Itchy bumps, blisters or raised areas
Outbreaks in exposed skin
Pain, redness and swelling
Chills, fever, and nausea
Diseases such as lupus or eczema
Metabolic conditions like pellagra and scurvy
Reactions to chemicals and medications
Photodermatitis is a phototoxic reaction entirely independent of the immune system. In other words, photodermatitis can occur in any individual, and prior sensitization or an intact immune system is not required. The ingredients needed to produce photodermatitis include temporal exposure to sunlight, especially ultraviolet radiation. In reaction to UV rays, certain chemicals, and drugs can cause sunburn, an eczema type reaction or hives. It may be related with an allergy like phytophotodermatitis where the trigger comes from plants.
Furocoumarins are photosensitizing chemical components produced by certain plants and consist of psoralens, 5-methoxypsoralens, 8-methoxypsoralens, angelicin, bergaptol, and xanthotal.
The natural sunlight emission spectrum reaching the earth ranges from approximately 270-5000 nm. This electromagnetic radiation consists of photons with a reciprocal relationship between the wavelength and the energy of the photons. Only light that is absorbed into the skin can cause a photochemical reaction. Within the light spectra, UV-A (320-400 nm) is responsible for the vast majority of photoreactions resulting in phytophotodermatitis.
The wavelengths of ultraviolet light that most efficiently produce phytophotodermatitis lie within the UV-A range and have peak activity at 335 nm. When a photon with the appropriate wavelength strikes a furocoumarin, the energy is absorbed, raising this chemical to a triple excited state from the ground state. Upon return to the ground state, energy is released in the form of heat, fluorescence, and/or phosphorescence, and a photoproduct may form.
Two distinct photochemical reactions have been described in phytophotodermatitis, which occur independently from each other. A type I reaction occurs in the absence of oxygen, whereas a type II reaction occurs in the presence of oxygen. These photochemical reactions damage cell membranes and DNA and result in DNA interstrand cross-linking between the psoralen furan ring and the thymines or the cytosines of DNA. During the type I oxygen-independent reaction, the RNA and nuclear DNA become fastened to the exposed ultraviolet-activated furocoumarins. Likewise, the oxygen-dependent reactions result in cell membrane damage and edema from activated furocoumarins. This results in activation of arachidonic acid metabolic pathways and in cell death (sunburn cells and apoptotic keratinocytes). Clinically, erythema, blistering, epidermal necrosis, and eventual epidermal desquamation occur. See the image below.
A post inflammatory pigment alteration may follow the acute phase of this phototoxic reaction. This alteration occurs primarily by 2 mechanisms. First, melanin, which is normally found in the epidermis, “falls” into the dermis and is ingested by melanophages. Secondly, an increased number of functional melanocytes and melanosomes are distributed in the epidermis following phytophotodermatitis and also account for the hyperpigmentation. This hyperpigmentation may serve as a protective mechanism against further UV injury. Clinically, this corresponds with irregular hyperpigmentation (or occasionally hypopigmentation resulting in dyschromia) seen as the end stage of the phototoxic reaction.
Usually, a direct physical examination is only needed for a confirmation. In rare cases, skin biopsy may be needed.
Prevention is the best cure in the cases of photodermatitis. Once you know you have the condition you can:
- Limit the sun exposure
- Use sunscreen with high SPF which is PABA free
- Cover up maximum with long sleeves, pants, hat etc.
In acute conditions, cool and wet dressings are applied externally. In extreme sensitivity cases, immunosuppressive drugs like azathioprine are used.
Multivitamins and minerals intake daily to correct nutritional deficiencies are also recommended in needed cases.
The prognosis is good with identification and avoidance of the offending agent, that is sunlight. Most commonly, photodermatitis is a localized cutaneous phenomenon developing initially in a burning sensation, which may be followed acutely by erythema and blistering. Eventually, the affected sites may desquamate and develop permanent hyperpigmentation or hypopigmentation. However, scarring is rare.
In rare cases, sun sensitivity can cause severe burns and can be fatal. Long term effects include scarring and an increased risk of skin cancer.
Disease & Ayurveda
There is not a direct mentioning about allergy to light in Ayurvedic texts. But the skin rashes seen in photodermatitis are eczematous and can be compared with Vicharchika. Also, the body of the person may be predominant with Pitta dosha as it is easier to get heated up and become sensitive to sunlight.
Diet consisting of food items with opposite potency
Unwholesome diet like chilichima with milk, certain cereals with milk etc.
Improper physical activities like exercise, sexual intercourse etc
Suppression of vomiting
And all other causes of Kushtha roga
Absence or excess sweating
Discolouration of skin
Lack of tactile sensation
Due to the causative factors like viruddhara, aama is formed and agni becomes manda. The vitiated doshas (mainly kapha) in this condition vitiate eachother and dhatus mainly rasa & rakta, and reaches skin. When exposed to the sunlight, these cause immediate reaction in the skin and develop into the rashes and other discomforts.
Blisters with pain, itching, red/black colour and exudation
Saadhya in new and uncomplicated cases
Yaapya in chronic cases
Treatment of kushtha (especially vicharchika) is alleviating the kleda or vitiated Kaphadosha. It should be done accordingly in each case. If the lesions are wet/oily and swelling is present, kaphadoshahara treatment should be done. If there is burning sensation, redness & severe inflammation, Pittadoshahara treatment should be administered. Other factors like body constitution, age, physical and mental strength of patient, digestion, season etc. also should be considered while treating the kushtha.
kshalana – washing with kashayas like aragwadhadikwatha or triphalakwatha
lepana – applying external medicines like nalparadi lepa, chandanadi lepa, kumaryadi lepa etc.
Vamana with madanaphalakwatha
Virechana with erandatailam, or avipathi choornam
Commonly used medicines
No home remedy is there to completely cure photodermatitis. Prevention is the best cure in these cases. But herbs that can help reduce the discomforts of the disease includes the following:
Applying ice packs can also be beneficial.
Light meals and easily digestible foods
Green gram, soups, buttermilk boiled with ginger, turmeric, curry leaves etc.
Freshly cooked and warm food processed with cumin seeds, ginger, ajwain etc
Heavy meals and difficult to digest foods – cause indigestion.
Junk foods- cause disturbance in digestion and reduces the bioavailability of the medicine
Carbonated drinks – makes the stomach more acidic and disturbed digestion
Refrigerated and frozen foods – causes weak and sluggish digestion by weakening Agni (digestive fire)
Milk and milk products other than buttermilk- Cause indigestion, increase Kaphadosha, can lead to obstruction in channels and respiratory problems.
Curd – causes vidaaha and thereby many other diseases
Red chilli and other pungent, hot and spicy food items.
Better to avoid exposure to excessive sunlight.
Maintain a regular food and sleep schedule.
Avoid sedentary lifestyle as it is one of the main causes of many diseases.
Avoid holding or forcing the urges like urine, faeces, cough, sneeze etc.
Most of skin diseases, gets worse with stress & lack of proper circulation. A regular exercise routine and yoga therapy is recommended in psoriasis cases for proper destressing & improved circulation.
All the exercises and physical exertions must be decided and done under the supervision of a medical expert only.
These statements have not been evaluated by the Food and Drug Administration, United States. This product is not intended to diagnose, treat, cure or prevent any disease. Please consult your GP before the intake.
Dr. Rajesh Nair, the co-founder and chief consultant of Ayurvedaforall.Com, is a graduate of prestigious Vaidyaratnam Ayurveda College (affiliated with the University of Calicut), Kerala, India. Additionally, he holds a Postgraduate Diploma in Yoga Therapy from Annamalai University.
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