Allergies is a broad term that describes what happens when your immune system reacts to a foreign substance as if it is harmful, even though it isn’t. Pollen, shellfish, insect bites, penicillin, red wine – the list of possible allergens, or substances that cause an allergic reaction, is long. Allergens can be inhaled (through the nose), ingested (through the mouth), or absorbed (through your skin or eyes). Allergies can affect anyone of any age, race or socioeconomic status. Allergic reactions are one of the most common chronic health conditions across the globe. 
Allergies can start at any age, and can also stop at any age. Typically, however, seasonal allergy sufferers (those allergic to grass or plant pollens that occur for one season each year) develop symptoms between the ages of two and 20. It is very possible, however, for allergies to any of hundreds of potential allergens to start later in life. There is no clear understanding of why this happens, but adult triggers can include:
Allergies and asthma often occur together in a condition called allergic asthma or allergy-induced asthma. In this case, the same substances that activate your allergy symptoms, such as pollen, pet dander, or specific food reactions, also cause asthma. 
While most allergic reactions to substances are simply annoying, they can also be life-threatening. Anaphylaxis, or an anaphylaxis reaction, happens when your immune system releases a flood of chemicals to combat the ‘invading’ allergen. These can cause you to go into shock where your blood pressure suddenly drops and your airways narrow, making it difficult or impossible to breath. 
The common symptoms of allergic reactions are caused by a chemical, called histamine, that is released by your immune system when it is trying to protect you. Managing your allergies is a combination of reducing your exposure to allergens and also reducing the amount of histamine that is circulating in your system. The Science section below provides detailed information about histamine and how it affects your systems.
Histamine is created when your body identifies allergens, which are substances that your immune system thinks are dangerous to your health. The first step in controlling allergies is to avoid the allergen, if possible. This is easy if you know what the allergen is and you know where it is so that you can avoid it. In many cases, however, this is not possible because you can’t always control your environment.
If you have tried to avoid allergens and are still suffering, a good first step is to try to reduce the amount of histamine circulating in your system. Many of the treatments for allergies focus on reducing histamine levels. Histamines are not just produced in your body – they are also found in or stimulated by many common foods and drinks. Reducing histamine levels can be done by lowering your intake of histamine-containing foods and avoiding histamine- stimulating foods (foods that increase the production of histamine in your body).  
If your favorite foods are on these lists, it can be depressing to imagine a lifetime limiting your intake. However, you can try a detoxifying approach, where you remove all of the possible trigger- and source-foods until your symptoms stabilize, and then begin to add your favorites back in one at a time. This will allow you to identify those foods that have an impact on YOUR system, as it is unlikely that all of the foods on this list will have the same effect on you.
At age 40 find a reliable, educated primary care provider familiar with recognizing and treating symptoms of perimenopause and menopause. The North American Menopause Society provides a list of menopause practitioners here.
Allergies are a complex reaction to many possible allergens. It is imperative that you talk to your healthcare provider about your allergies and make sure they are aware of any steps you are taking (such as reducing certain foods, using antihistamines, etc.) There are some medical treatments for allergies, but they vary widely depending on the allergen and need to be tailored to fit your circumstances. Your healthcare provider can prescribe or recommend (if they are over-the-counter) some allergy medications.
If your allergies are severe, or have become severe, immunotherapy may be helpful. This treatment involves having a series of injections that contain purified allergen extracts. These injections are taken over a period of years and are usually used to treat hayfever, allergic asthma, conjunctivitis as a result of allergens or stinging insect allergies. Allergy shots are not used to treat food allergies. The best option for people with food allergies is to strictly avoid that food.
Considerations about allergy shots include:
Your healthcare provider may also suggest increasing the levels of the enzyme diamine oxidase (DAO) that breaks down histamine in your system. This is a response to histamine intolerance (where you have high levels of histamine circulating in your body all the time), rather than ordinary allergies, however, the result can be the same – higher levels of DAO means lower levels of histamines. Increasing DAO enzyme levels can be achieved with dietary supplements. Taking any supplements should only be done with the approval of your healthcare provider as many supplements contain ingredients that can have a profound effect on other body systems or interfere with medications that you are already taking.
If you have had, or are concerned about having an extreme allergic reaction, called anaphylaxis, you should consult your healthcare provider and consider carrying emergency epinephrine. An epinephrine shot, in the form of a EpiPen or other pre-filled injectors, should be available for use – it will reduce your immediate reaction long enough for you to get emergency treatment.
Your body is constantly working to protect you from external pathogens like bacteria and viruses. To do this, your body mounts an immune response that can come via several different pathways. Your immune response can be either innate (that you were born with), or adaptive or acquired (immunity following exposure to the pathogen). Your innate immune system includes physical barriers (like your skin), chemical barriers (like tears), and cellular barriers (like general cellular immune responses that identify and destroy any substance that is a potential pathogen). Adaptive, or acquired immunity develops during your lifetime in response to a specific pathogen. 
The adaptive immune response involves special lymphocytes called T and B lymphocytes, both of which mature in the bone marrow and produce antibodies (a specialized protein cell) in response to the antigens (a substance that causes the body to make a specific immune response to allergens, for example).
When a B lymphocyte (or B cell) meets up with an antigen it doesn’t recognize, it makes antibodies that are specific to the antigen, like a customized defender that will only respond to a specific invader. Not only do B cells produce the antibodies, they also create memory cells. These survive for long periods of time (decades or in some cases, your whole life) with the sole purpose of detecting specific pathogens in the future.
T lymphocytes, or T cells, originate in the bone marrow and mature in the thymus. T cells work to remove the pathogens from the body. When a pathogen enters a cell in the body, the T-cells notify the B-cells to make an antibody, and also activate a specialized type of T cell called a killer T cell that kills any cells invaded by the pathogen. In addition to cells invaded by pathogens (either a bacterium, a microorganism, or a virus), killer T cells also target cancer cells.
Adaptive immunity can be active or passive. Active immunity happens when your own body’s B cells generate the antibodies needed to identify the pathogen in the future. This can happen either when you get sick naturally and make antibodies, or when you receive a vaccine containing the pathogen, which then triggers your immune system to make antibodies. Passive immunity happens when you receive the antibodies from another source. This can be either through your mother’s milk when you were nursing, or through the injection of existing antibodies from a different source. 
|Innate Immunity||Adaptive Immunity|
|Time to see an effect||immediately – no time delay||over time|
|Type of pathogen||nn-specific; general||one specific pathogen|
|Type||physical; chemical; cellular||active; passive|
|Types of cells involved||macrophages, neutrophils, eosinophils, basophils, mast cells, dendritic cells, and gamma-delta T cells, and killer T cells||B cells (or B lymphocytes); multiple types of T cells (or T lymphocytes), including helper T cells, suppressor T cells, gamma-delta T cells, and killer T cells|
|Other names||natural immunity; genetic immunity||acquired immunity|
|How long it is effective||lifelong||variable – depends on the pathogen. Can be months, years, decades, or lifelong|
Your immune system is an incredibly complex system that works to defend your body against any pathogens, which are bacteria, viruses, or other microorganisms that can cause disease. When a pathogen enters your body – into your blood when you have a cut, or in through your nose when you inhale for example – your immune system reacts to destroy it.
Allergic reactions happen when a person with an allergy encounters a harmless substance such as dust, animal dander, or pollen. Their immune system mistakes the substance as dangerous and reacts by producing antibodies called Immunoglobulin E (IgE) that “attack” the allergen. These antibodies travel and attach to specialized cells, called mast cells, which respond to the IgE by releasing chemicals that cause an allergic reaction. This reaction usually causes symptoms, such as wheezing, itching, runny nose, watery or itchy eyes, and/or hives in the nose, lungs, throat, or on the skin. 
Each type of IgE is specialized to detect one type of allergen. If you are only allergic to cat dander it means you only have the IgE antibodies specific to cat dander. If you have allergic reactions to multiple allergens it is because you have multiple types of IgE antibodies – each one specific to one of your allergens. 
Many people recognize the term ‘antihistamine’ because it is the name of a type of medicine that is often used when we have allergic reactions. What isn’t so familiar is the term histamine, which is what antihistamines are fighting against (anti- means ‘opposed to’). Histamine is a type of neurotransmitter produced by your immune system to fight off allergens, and it is the cause of skin, nose, eye, throat and lung irritation that is so common in allergic reactions. Additionally, histamine plays an important role in many different body systems.  
Histamine is produced in specialized types of white blood cells called mast cells, eosinophils, or basophils. These cells are all key components of your innate immune system as shown in the innate vs adaptive immunity table. Mast cells are found throughout the body including on your skin, in your lungs, nose, mouth and gut, and also in your blood. When mast cells release histamine, these neurotransmitters act to increase blood flow to the area where the allergen is located, making it swell, itch and become red and inflamed. This inflammation is part of your immune system’s overall response to getting rid of allergens and healing any tissue that was damaged. 
For example, say you breathe in some dander from your new puppy. If your immune system detects this dander as an allergen, it will instruct the mast cells to release histamine. The histamine will flood your nose, telling your mucous membranes to make more mucus, and just like that, you have a runny or stuffy nose. If mucus builds up in your airways, they can narrow and you may sneeze or even start to wheeze. Mast cells in your gut react to food allergens, mast cells on your skin react to any allergen that touches your skin and so on.
Histamine intolerance happens when you have too much histamine circulating in your system. It shares many of the same symptoms driven by the presence of histamine, but histamine intolerance can also cause headaches or migraines, fatigue, digestive issues, nausea or vomiting.  
Histamine gets released from mast cells as part of your immune response. Mast cells, however, also have receptors to bind both estrogen and progesterone, causing both of these hormones to also play a role in the release of histamine. Estrogen stimulates the release of histamine in the same way that Immunoglobulin E (IgE) stimulates the release of histamine – by binding to the mast cells. Not only does estrogen cause histamine release, it also blocks the action of the enzyme, called diamine oxidase (DAO), that breaks down histamine. So estrogen increases histamine levels in your body by both creating more of it, but also by keeping it circulating throughout the body. Histamine, in turn, stimulates the ovaries to make even more estrogen. This can turn into a vicious cycle of estrogen causing more histamine causing more estrogen. Progesterone, which also binds to mast cells, acts to reduce histamine levels by helping to break down the enzyme DAO. As your hormones begin to fluctuate during the menopausal transition, levels of histamine circulating in your blood will also fluctuate. This is why many women start to have allergic reactions or see their existing allergies get worse during the menopausal transition.  
The organs in your body that are involved in your immune system are called the lymphoid organs and they act to grow, develop and release a type of white blood cell called a lymphocyte. Your lymphoid organs include your:
Nope, this won’t work and is a terrible idea! Once your immune system is sensitized to an allergen, you will keep having allergic reactions when you are exposed to that allergen. Allergy shots, or immunotherapy, do desensitize you to allergens, but this must be done under the care of an allergy specialist who will control the quantity, quality and time intervals of these shots. Talk to your healthcare provider for information if you think this may be an approach you are interested in.
Some allergic reactions can be deadly. An anaphylactic reaction happens when a very large amount of histamine is released into your system at once causing a massive inflammatory reaction. Symptoms include difficulty breathing, wheezing, stomach pain and cramps, diarrhea, anxiety, swelling of the feet, hands, lips, eyes, and possible loss of consciousness. Death often occurs when airways swell shut. Portable epinephrine injectors, (one common brand is called the EpiPen) are designed to auto inject a hormone called epinephrine, which works rapidly and stimulates the heart, raises blood pressure and reduces swelling in the throat, lips, and face. In Canada, EpiPens are available with or without a prescription. Ask your healthcare provider for advice on whether you should have one available.
If you know you will be coming into contact with a known allergen (visiting your friend who has a dog that you react to, for example), take your allergy medication (often an over-the-counter antihistamine) before you go. This can actually prevent any allergic reaction at all.
Absolutely not true, as most allergy sufferers can tell you. Some individuals seem to have more sensitive reactions than others and can have multiple allergies to multiple different allergens. Not all of these allergies will occur at the same time, nor will they all last the same amount of time.
Some allergies do, in fact, stick around for your whole life. The good news though, is that many allergies fade away as time passes. It all depends on the allergen and your individual system and sensitivities.
Developing allergies in adulthood is relatively common, and in fact nearly half of adults with food allergies had those allergies start in adulthood. While it is very common for adult-onset allergies to happen in your 20s and 30s, perimenopause is a time when many women start to suffer new allergies or have increasingly problematic symptoms to existing allergies. This is caused by the interactions of estrogen and progesterone with the immune system, because estrogen and progesterone bind to the parts of the immune system that trigger allergic reactions.
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