Allergy symptoms occur when your immune system overreacts to an allergen—something that usually is harmless, such as plant pollen, dust mites, molds, insect stings or food. If you have an allergy, your immune system acts as if the allergens were dangerous, releasing a chemical called histamine that causes allergy symptoms.
If the allergen is something you breathe in from the air, your reaction will most likely affect your eyes, nose and lungs.If it's something you eat, it may affect your mouth, stomach and intestines. Food allergies also can cause skin rashes or even asthma symptoms.
Allergy symptoms will vary depending on the type of allergen.
Allergic conjunctivitis manifests as 3 major forms AND WEEDS
Seasonal allergic conjunctivitis (SAC)
This is the most common form and occurs seasonally as plants pollinate and produce air borne allergens molds and weeds.
Perennial allergic conjunctivitis (PAC)
Individuals with PAC have symptoms that last the whole year. Common household allergens such as dust mite, cockroaches, and pet dander are responsible for the symptoms.
Vernal keratoconjunctivitis (VKC)
VKC is a chronic bilateral inflammation of the conjunctiva that most often occurs in spring and fall (hence called spring catarrh). It has the potential to permanently damage vision.
The patients usually present with ocular itching, redness, burning, tearing and photophobia (inability to tolerate bright light). Some of them may develop allergic shiners (dark circles below the eyes due to repeated rubbing).
Allergic Rhinitis either seasonal or perennial affects upto 25% of the population.Though it is considered a trivial and inconsequential disease, it is a cause of significant disability and cost to society.
The common symptoms include sneezing, nasal congestion, nasal itching, and running nose. Complications include otitis media, Eustachian tube dysfunction, and acute and chronic sinusitis.
Allergic rhinitis can be associated with a number of comorbid conditions, including asthma, atopic dermatitis, and nasal polyps. Symptoms such as fatigue, drowsiness (due to the disease or to medications), malaise, irritability, mood, cognitive and sleep disturbances and dental mal-occlusion can frequently lead to significant impairment of quality of life.
Seasonal allergic rhinitis: (Hay Fever)
Grass and tree pollens and some fungi trigger hay fever, usually during spring (March to June). These people do not have the typical allergy facies but have seasonal symptoms along with puffiness of eyes and eyelids with nasal membrane swelling.
Perennial allergic rhinitis: ('permanent cold')
It is typically caused by allergens within the home such as house dust mite droppings, cat and dog dander, horse's hair and cockroach droppings but can also be caused by outdoor allergens that are present year-round. These patients have subtle symptoms of rhinitis along with loss of taste and smell sensation and allergic facies is seen in these types of patients.
Asthma is one of the most common chronic diseases worldwide. One in every twenty children under the age of 6 yrs is asthmatic. Urbanization, air pollution, passive smoking, and change in exposure to environmental and morbidity of the disease.
Environmental allergens implicated in allergic asthma are house dust mites,animal allergens [especially cat and dog], cockroach allergens, bird feathers, some foods and fungi. Pollutants such as cigarette smoke, vehicle exhaust fumes, and certain chemicals can also trigger an attack of asthma.
The patients present with cough, wheezing, shortness of breath, chest tightness, sputum production and decreased exercise tolerance.
The true incidence of food allergy in India is not known. In the US about 4 million people have a true food allergy. It needs to be differentiated from food intolerance (due to enzyme deficiency) and food poisoning (due to preformed toxins in the food) both of which are not immunologically mediated.
Peanuts, walnuts, other tree nuts, shrimp, lobsters, crabs and shellfish are usually implicated in food-induced allergies. 90% of the IgE mediated food allergies in to cows milk protein, hen's egg white, wheat, codfish, peanut and soya bean.
Typical symptoms observed in food-induced allergies include oropharyngeal pruritus (itching tongue, lips and throat), vomiting, abdominal cramps and diarrhea. Anaphylactic reaction to food allergens can involve the respiratory tract leading to angioedema (e.g., laryngeal edema), stridor, cough, dyspnoea, wheezing and dysphonia. It can also cause hypotension, eczema, urticaria and hives and may even lead to death.
Contact allergies include two distinct reactions:
Allergic contact dermatitis (ACD)
Urticaria, commonly known as hives, affects 15-20% of the general population. It can either be acute or chronic. The acute form of urticaria lasts less than 4-6 weeks, and the chronic form lasts more than 4-6 weeks.
Urticaria is characterized by red, blanching, raised, palpable wheals (the typical 'wheal and flare' response) and can appear anywhere in the body. Erythema and edema of the superficial dermis is seen.
The most common precipitating allergens include
- Foods: (e.g., shellfish, fish, eggs, cheese, chocolate, nuts, berries, tomatoes)
- Cosmetics and toiletries: perfumes, detergents, lotions, creams, hair dyes and nail polish
- Exposure to pets (dander), dust, mold, chemicals, plants,
- Contact with nickel (e.g., jewelry, jeans stud buttons), rubber (e.g., gloves, elastic bands), latex and industrial chemicals
- Drugs (e.g., penicillins, sulfonamides, salicylates, NSAIDS, codeine).
Allergic Contact Dermatitis: