An allergy is a hypersensitive immune response or reaction to substances that comes in contact with the body or enters the body and they are usually not harmful. Some examples of these substances are pet dander, pollen or bee venom.

Any substance that causes an allergic reaction is called an “allergen” and they can be found in food, drinks or the environment for which most of them are harmless, i.e. the majority of people are not affected by them.

If one is allergic to a substance, the immune system reacts to it as if it were a pathogen (a foreign harmful substance), and tries to destroy it.

• Allergies are the result of an inappropriately large immune response

• Some of the most common allergens are dust, pollen, drugs and nuts

• Allergies have a range of symptoms that can include sneezing, peeling skin and vomiting

• Anaphylaxis is a serious allergic reaction that can be life-threatening

• There are a number of risk factors for allergies, including a family history

• If you already have an allergy, you are more likely to develop an allergy to something else

• In theory, any food has the potential to be an allergen

• To diagnose an allergy, a clinician may take a blood sample.


Allergies are very common and both genes and environment play a role in it. The immune system normally protects the body against harmful substances, such as bacteria, fungi, toxin and viruses, hence reacts to theses as though they are harmful. However, allergens are usually not harmful and do not pose a problem but the immune system has simply become oversensitive to these substances. When the immune system recognizes an allergen, it reacts to it and releases immunoglobulin E (IgE), a type of antibody. IgE is released to destroy the allergen, hence causes chemicals in the body to be produced. Chemicals such as histamines and these chemicals cause the allergic reaction.

Histamine causes tightening of the muscles, including those in the airways and the walls of blood vessels. It also makes the lining of the nose produce more mucus. People with allergies blame the allergen for their symptoms like the food, drugs etc, however, the allergens are not harmful thus the problem is not the allergen but the allergic person’s immune system which mistakes harmless substances for harmful ones. Some common allergens include:

• Drugs (Penicillin, Salicylates (a salt of salicylic acid commonly found in many medications) including aspirin and Sulfonamides.

• Food (any food can cause an allergy. The eight foods most likely to cause allergies are eggs (especially egg-white, albumen), fish, milk, nuts from trees, peanuts (groundnuts), wheat, soy, and shellfish. Other foods that can cause allergies include corn (maize), celery, pumpkin, beans and sesame.

• Dust,

• Insect venom

•Mold spores; Alternaria, Aspergillus, Aureobasidium (Pullularia), Cladosporium (Hormodendrum), Epicoccum, Fusarium, Helmin thosporium, Mucor, Penicillium, Rhizopus.

• Pets and other animal dandler; (cats, dogs etc)

• Pollens which causes hay fever; Grass (the most common cause of hay fever), Trees (oak, ash, cedar, willow, and hazel), Weeds (mugwort and ragweed).
Others include wool, fur, household chemicals, latex, metals etc. Some people have allergy-like reactions to hot or cold temperatures, sunlight, or other environmental triggers. Sometimes, friction (rubbing or roughly stroking the skin) will cause symptoms.


Before we talk about the symptoms, let’s talk about some of the risk factors of allergies. A risk factor in medicine is something that raises the risk of developing a disease or condition and this can come from something a person does. For example, smoking is a risk factor for lung disease. It can also be something you are born with. Another is if a mother had breast cancer, her daughter has a higher risk of developing breast cancer too. A family history of breast cancer is a risk factor. Below are some risk factors associated with allergies:

• A family history of asthma – if your parents, grandparents or siblings have/had asthma, your risk of having an allergy is higher and people with asthma are significantly more likely to develop allergies

• A family history of allergies – if a close relative has/had an allergy, your risk of having an allergy yourself is greater

• Being a child – a child is much more likely to have an allergy than an adult. On a positive note, this means that many children outgrow their allergies

• Not enough sunlight exposure – scientists from the European Centre for Environment & Human Health, together with researchers from various Australian centers found that children living in areas with less sunlight had higher rates of allergies

• Having an allergy – if you already have an allergy, there is a greater risk that you will develop an allergy to something else.

• C-section babies – a team from the Henry Ford Hospital reported that C-section babies have a considerably higher risk of developing allergies compared to those born naturally

• Chemicals used in water purification – Dr. Elina Jerschow, a fellow of the American College of Allergy, Asthma and Immunology, said that pesticides in tap water could be partly to blame for the increased food allergy rates in the USA.


When a person with an allergy comes into contact with an allergen, the allergic reaction is not immediate. The immune system gradually builds up sensitivity to the substance before overreacting to it.

The immune system needs time to recognize and remember the allergen. As it becomes sensitive to it, it starts making antibodies to attack it – this process is called sensitization.
Sensitization can take from a few days to several years. In many cases the sensitization process is not completed and the patient experiences some symptoms but never a full allergy.

When the immune system reacts to an allergen, there is inflammation and irritation. Signs and symptoms depend on the type of allergen. Allergic reactions may occur in the gut (digestive system), skin, sinuses, airways, eyes, and nasal passages.

1. Symptoms of allergies from dust and pollen include the following: blocked nose, itchy eyes, itchy nose, runny nose, swollen eyes, watery eyes, and cough. On the skin, we have skin reactions such as eczema, flaking skin, itchy skin, peeling skin, red skin, and rashes.

2. Symptoms from food allergies include the following reactions: Vomiting, Tongue swelling, Tingling in the mouth, Swelling of the lips, Swelling of the face, Swelling in the throat, Stomach cramps, Shortness of breath, Rectal bleeding (in children, rare in adults), Itchiness in the mouth, Diarrhea, Anaphylaxis (a very severe, often life-threatening allergic reaction).

3. Symptoms from insect sting are: Wheezing. Swelling where the sting occurred, Sudden drop in blood pressure, Skin itching, Shortness of breath, Restlessness, Hives (a red and very itchy rash that spreads), Dizziness, Cough, Chest tightness, Anxiety, Anaphylaxis.

4. Symptoms of allergic reaction to medication include the following: wheezing, swollen tongue, swollen lips, swelling of the face, skin rash, itchiness, and anaphylaxis.

Symptoms of anaphylaxis

Anaphylaxis is a serious allergic reaction of rapid onset. It can be life-threatening and must be treated as a medical emergency. This type of allergic reaction presents several different symptoms which can appear minutes or hours after exposure to the allergen. If the exposure is intravenous, onset is usually between 5 to 30 minutes. A food allergen will take longer.

Researchers from the University of Manitoba, Canada, reported in The Journal of Allergy & Clinical Immunology that the most commonly affected areas in anaphylaxis are the skin (80-90%), respiratory (70%), gastrointestinal (30-45%), cardiovascular 10-45%) and the central nervous system (10-15%). In most cases two areas are affected simultaneously.

Anaphylaxis – skin symptoms

Hives all over the body, flushing and itchiness. The affected tissues may also become swollen (angioedema). Some patients may experience a burning sensation on the skin. In about 20% of cases, there is swelling of the tongue and throat. If the skin has a strange bluish color, it could be a sign of hypoxia (lack of oxygen). Some patients may experience a runny nose.

The membrane that covers the front of the eye and the inside of the eyelid (conjunctiva) may also become inflamed.

Anaphylaxis – respiratory symptoms

• Shortness of breath

• Wheezing – caused by bronchial muscle spasms

• Stridor – a high-pitched vibrating wheezing sound when breathing. Caused by upper airway obstruction due to swelling

• Hoarseness

• Odynophagia – pain when swallowing

• Cough.

Anaphylaxis – cardiovascular symptoms

Coronary artery spasm – sudden tightening of the muscle in the artery wall (temporary) due to cells in the heart that release histamine. This can lead to myocardial infarction (heart attack), dysrhythmia (abnormal heart rhythm), or cardiac arrest (heart stops).
Low blood pressure can cause the heart rate to accelerate. In some cases a slow heart rate can occur as a result of low blood pressure (Bezold-Jarisch reflex).

Patients whose blood pressure suddenly drops can feel lightheaded and dizzy. Some may lose consciousness. In some rare cases, the only sign of anaphylaxis might be low blood pressure.

Anaphylaxis – gastrointestinal symptoms
• Abdominal cramps
• Diarrhea
• Vomiting
• Loss of bladder control
• Pelvic pain (like uterine cramps).


First the patients will be asked questions as regard to the allergy symptoms, questions such as patient when they occur, how often and what seems to cause them, family history as regard to allergies is also required. After this, it is recommended that to carry out some tests to determine the main cause of the allergy.

Below are some examples of allergy tests:
• Blood test – to measures levels of IgE antibodies released by the immune system. This test is sometimes called the radioallergosorbent test (RAST)

• Skin prick test – also known as puncture testing or prick testing. The skin is pricked with a small amount of a possible allergen. If there is a skin reaction – itchy, red and swollen skin – it may mean there is an allergy

• Patch test – for patients with contact dermatitis (eczema). Special metal discs with trace amounts of a suspect allergen are taped onto the back. The doctor checks for a skin reaction 48 hours later, and then again after a couple of days.
The National Health Service says that commercial allergy-testing kits are not recommended and that patients should have these tests done by specialized health care professionals.


The most effective treatment and management of an allergy is to avoid exposure to the allergen. However, sometimes it is not possible to completely avoid an allergy. A person with hay fever cannot avoid exposure to pollens, unless he/she closes all the windows in the house and never goes out. Even then, there is a risk of other people bringing pollen into the house. It is also important to educate patients so that they know how to identify their allergenic foods properly.

These said, severe allergic reactions such as anaphylaxis need to be treated with a medicine called epinephrine. It can be life-saving when given right away. If you use epinephrine, call 911 and go straight to the hospital.

There are several types of medications to prevent and treat allergies. Which medicine your doctor recommends depends on the type and severity of your symptoms, your age, and overall health.

Illnesses that are caused by allergies (such as asthma, hay fever, and eczema) may need other treatments. Medications that can be used to treat allergies include:


These are histamine antagonists. They block the action of histamine, a chemical released in the body as part of an allergic reaction. Some antihistamines are not suitable for children. They are available over-the-counter and by prescription in many forms such as;
 Capsules and pills
 Eye drops
 Injection
 Liquid
 Nasal spray

Corticosteroids or Steroid sprays

These are anti-inflammatory medications that are applied to the inside lining of the nose. Corticosteroid sprays help reduce nasal congestion. They are available in many forms, including:
 Creams and ointment for the skin
 Eye drops
 Nasal spray
 Lung inhaler

Persons with severe allergic symptoms may be prescribed corticosteroid pills or injections for short periods.


Decongestants help relieve a stuffy nose. Some patients say they help with a blocked nose in cases of hay fever, pet allergy or dust allergy. Decongestants are short-term medications. However, do not use decongestant nasal spray for more than several days because they can cause a rebound effect and make the congestion worse. Decongestants in pill form do not cause this problem. People with high blood pressure, heart problems, or prostate enlargement should use decongestants with caution.

Leukotriene receptor antagonists (anti-leukotrienes):

Leukotriene inhibitors are medicines that block the substances that trigger allergies. Person with asthma and indoor and outdoor allergies may be prescribed these medicines when other treatments have not worked. Anti-leukotrienes block the effects of leukotrienes, chemicals that cause swelling. Leukotrienes are released in the body when there is an allergic reaction

Allergy Shots

Allergy shots (immunotherapy) are sometimes recommended if you cannot avoid the allergen and your symptoms are hard to control. That is to say, it is used in cases of severe allergies. Allergy shots keep your body from over-reacting to the allergen. You will get regular injections of the allergen. Each dose is slightly larger than the last dose until a maximum dose is reached. These shots do not work for everybody and you will have to visit the doctor often.

Sublingual Immunotherapy Treatment (Slit)

Instead of shots, medicine put under the tongue may help for grass and ragweed allergies.


As earlier said, this is a severe allergic reaction, a medical emergency and should be treated immediately. The patient may require resuscitation, including airway management, supplemental oxygen, intravenous fluids and close monitoring. The patient, who often has to be hospitalized, will need an injection of adrenaline (epinephrine) into the muscle. Antihistamines and steroids are often used as adjuncts.
After the patient has been stabilized, doctors may recommend they remain in hospital under observation for up to 24 hours in case of biphasic anaphylaxis. Biphasic anaphylaxis is the recurrence of anaphylaxis within 72 hours with no further exposure to the allergen.

Patients who have had severe allergic reactions should carry an epinephrine autoinjector with them, which may include the EpiPen, EpiPen Jr, Twinject, or Anapen.
Many doctors and health authorities advise patients to wear a medical information bracelet or necklace with information about their condition.


Even though treatments can help alleviate allergy symptoms, patients will need to try to avoid exposure to specific allergens. In some cases this is not easy. Avoiding pollen in late spring and summer is virtually impossible, even the cleanest houses have fungal spores or dust mites.

If you have friends or family with pets, avoiding them might be difficult. Food allergies can be challenging to manage, because traces of allergens can appear in the most unlikely meals.

Reducing your exposure to dust mites

  •  Go for hard floor surfaces rather than carpets
  • Replace your window curtains with roller blinds.
  • Regularly vacuum cushions, chairs, and soft toys. Where possible, wash them at a high temperature setting.
  • Do not use woolen blankets or feather pillows.
  • Instead of dry dusting, which can scatter allergens into the air, wipe surfaces with a  damp cloth.

Preventing allergies to cats and dogs

It is not the pet itself but proteins found in its urine, saliva, flakes of dead skin or hair that can cause allergic reactions. If you cannot avoid being in contact with a pet you are allergic to, see if you can come to an arrangement where it is not allowed into certain parts of the house, for example upstairs. Do not allow the pet into your bedroom.

Grooming a dog or cat outside regularly can help (try to get somebody to do this for you). The pet’s bedding and soft toys should be washed at a high temperature setting regularly. If you have to go into a pet owner’s house, taking an antihistamine medication beforehand may help.

Preventing mold spore allergy

  • Test your house for mold.
  • Check the plumbing in your house. Leaks create damp areas which are ideal environments for molds.
  • You can probably clean small moldy areas yourself. An environmental service can help clear mold from difficult-to-get-to areas.
  • If mold is detected inside drywall, it must be cut out and replaced.
  • Make sure all hard surfaces are mold free.
  • Avoid having carpets in damp areas of your house.
  • Replace moldy tiles or carpets.
  • Make sure your bathrooms are well ventilated.
  • Dehumidifiers and air conditioners help keep the house dry. Make sure filters are changed regularly.

Preventing Pollen allergies (hay fever)

Use OTC antihistamines. For many patients they are very effective at reducing the classic symptoms of hay fever. Go for the more recent products which are less likely to cause drowsiness.

Keep all the doors and windows in your house closed. This helps prevent pollens and outdoor molds from entering.

Go out as little as possible in the morning or when pollen counts are high. On windy days it is better to stay in. Pollen counts tend to be higher between 5am and 10am.

Keep the windows of your car closed when you are traveling. Make sure the air filter is regularly serviced.

If you have been out, change clothes and have a shower when you are back home. Pollen can gather on clothes, skin and hair.

The following measures can also help reduce the severity and frequency of hay fever symptoms:

  • Stay away from very grassy areas, such as fields and parks.
  • Avoid drying your clothes and sheets outside when pollen counts are high.
  • Always be aware of the pollen count in your area.
  • If you are also allergic to cats and dogs, stay away from pets when pollen levels are high. People who are allergic to pets may find their ragweed allergy symptoms get worse when exposed to dogs or cats.

Preventing food allergies

Before considering buying and eating a particular food, read the list of ingredients on the label. A considerable number of prepared foods contains allergens, such as milk, eggs or peanuts.

Simple hygiene – straightforward cleanliness measures can help reduce your risk of coming into contact with a food allergen. If you are allergic to peanuts, for example, washing your hands with soap and water will remove all or most traces of the allergen. Keeping working surfaces clean with a good household cleaner also helps.

It can be especially difficult to avoid food allergens when eating out. So it is mandatory you explain clearly to the waiter (and the chef if you can) that you have a food allergy and how important it is for you to avoid certain food(s).

Preventing anaphylaxis

If you are vulnerable to anaphylaxis, a severe allergic reaction, make sure you have an “allergy action plan”.

Parents should inform their school, day care center, etc., regarding their child’s allergy and what to do in an anaphylactic emergency.

Tell your work colleagues and friends so that they can help you in an emergency.
You should always carry an epinephrine autoinjector, e.g. an EpiPen, and wear a medical alert bracelet. It is advisable to receive professional counseling on how to avoid triggers.

Coined from Christian Nordqvist (2016), Allergies: Causes, Diagnosis and Treatment

Dermatology Research and Practice, National Institute for Health and Clinical Excellence (NICE), American College of Allergy, Asthma and Immunology, British Society for Allergy & Clinical Immunology (BSACI), Allergy U.K.


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