Allergy Causes and Prevalence
Causes of allergy are very broad but research shows the following are culprits for allergy onset and progression:
- Westernization of countries
- Smoking and exposure to cigarette smoke
- Birth and breastfeeding factors
- Mom’s diet during pregnancy
- Solid food introduction
- Different types of infection and early infection
- Antibiotic treatment
- Home environment such as having siblings and early exposure to household pets
- Gut microbiome (bacteria), virome (viruses living in the gut), and gut parasites
The World Health Organization (2012) states the following on prevalence worldwide:
- Worldwide, sensitization (IgE antibodies) to foreign proteins in the environment is present in up to 40% of the population.
- Worldwide, the rise in prevalence of allergic diseases has continued in the industrialized world for more than 50 years.
- Worldwide, sensitization rates to one or more common allergens among school children are currently approaching 40%-50%.
Allergies: What are they and how do they manifest?
Allergic reaction is when the body’s immune system becomes over reactive to a seemingly benign trigger like pollen, dander, or dust. The immune system is used to fight war against bacteria and viruses, using the body as it’s battleground. When white blood cells (immune cells) are overactive they become ‘trigger happy’ when they come in contact with potential allergens like ragweed or goldenrod for instance. The immune cell then sends out many pro-inflammatory cytokines, or ‘bullets’ to keep with the analogy. These cytokines then cause the tissues that they hit to be swollen, more permeable so fluid and mucous can leak through, and hypersensitive to another potential allergen. This is what happens in the eyes, ears, nose, airways, and skin in response to allergy.
Immune cells that release killer bullets in response to allergens are activated by large proteins called immunoglobulins or antibodies. Antibodies act like drug dogs in the blood stream, floating around and trying to detect bacteria/viruses. They then present the allergen to the white blood cell to be destroyed. This is important to know due to the fact that immediate, histamine reactions as discussed above are Immunoglobulin E (IgE) type, and delayed type sensitivities (3-4 days after allergen exposure) are IgG mediated. IgA is in the saliva, tears, gut, and breastmilk. It is the first antibody and immune protection we get as babies. This is why so many allergies can develop in infancy, particularly when gut health isn’t good which will be discussed below.
• Made to bacteria and virus
• Highest level in blood
• Half-life of 23 days (longer in the bloodstream)
• Made to worms and parasites
• Mast cell
• Half-life of 2 days (shorter in the bloodstream)
• Th2 response
• Made to Food
• Found in secretions
• First antibody – saliva
• Treg response
1) Lee N, Kim W-U. Microbiota in T-cell homeostasis and inflammatory diseases. Experimental & Molecular Medicine. 2017;49(5):e340-. doi:10.1038/emm.2017.36.
2) Kim D, Zeng MY, Núñez G. The interplay between host immune cells and gut microbiota in chronic inflammatory diseases. Experimental & Molecular Medicine. 2017;49(5):e339-. doi:10.1038/emm.2017.24.
3) Tun HM, Konya T, Takaro TK, et al. Exposure to household furry pets influences the gut microbiota of infant at 3–4 months following various birth scenarios. Microbiome. 2017;5:40. doi:10.1186/s40168-017-0254-x.
The Gut: Using it as leverage for the histamine response
The gut is a huge source of neurotransmitters (think brain chemicals, mental health, and behaviour), immune cells, and cytokines (bullets).
Watch this clip to see how the microbiome in the gut interacts with our immune system and brain: https://www.youtube.com/watch?v=VzPD009qTN4
A type of white blood cell called the B cell makes antibodies to circulate and tag allergens. T-helper cells (Th cells) are another immune cell which helps B cells make antibodies, and they release cytokines (bullets) as well.
Th cells can be classified into Th1, Th2, Th17 and regulatory T (Treg) groups based on their different cytokine makeup. The intestine is one of the earliest organs to prime the body’s immune cells due to their immune centres called GALT and MALT. Gut Associated Lymphoid Tissue and Mucosa Associated Lymphoid Tissue respectively. This is why the small intestine is important to keep healthy, and why research shows that probiotic supplementation can impact allergy response.
- Th1 response in the body is mounted to bacteria and viruses (the ‘good’ response).
- Th2 is the main allergy response (the ‘bad’ one), including for allergic asthma.
- Th17 is the primary response for asthma and molds (also considered ‘bad’).
- Treg is T regulatory cells and they are also good as they can shut down an overactive Th2 or Th17.
The key is to create balance between Th1 and Th2, and in allergies Th2 response is usually high. Things that drive Th2 immune response can make other infections worse.
Driving the Th1 immune response can be done with an anti-inflammatory diet, certain herbs, and probiotics. Probiotics plant good bacteria seeds into the gut microbiome and crowd out bad bugs, or ‘weeds’.
- Bifido bacteria probiotics drive Treg and is big in breastmilk, our first immunity as an infant.
- Lactobacilli probiotics drive Th1 and Treg.
- Marijuana increases Th2
- Constant stress decreases Th1
Studies have shown the following with regards to probiotic supplementation:
- Prevention of eczema with probiotics works until age 2 years and extend until 4 years. L. rhamnosus shows the most consistent effects, especially when combining pre and postnatal administration. (1)
- Lactobacillus rhamnosus, Propionibacterium freudenreichii shermanii, and Bifidobacterium animalis lactis might shut down mast cell allergy-related activation by lowering IgE and histamine receptor genes. (2)
- In a 12 week trial, supplementation with probiotics in 50 children significantly reduced eczema and the dose of topical corticosteroid creams. The strains were Bifidobacterium lactis, B longum, and Lactobacillus casei. (3)
1) Kuitunen M. Probiotics and prebiotics in preventing food allergy and eczema. Curr Opin Allergy Clin Immunol.2013Jun;13(3):280-6.doi: 10.1097/ACI.0b013e328360ed66.
2) (In Vitro Study) Oksaharju A, Kankainen M, Kekkonen RA, et al. Probiotic Lactobacillus rhamnosus downregulates FCER1 and HRH4 expression in human mast cells. World Journal of Gastroenterology?: WJG. 2011;17(6):750-759. doi:10.3748/wjg.v17.i6.750.
3) Vicente Navarro-Lopez MD, et al. Effect of Oral Administration of a Mixture of Probiotic Strains on SCORAD Index and Use of Topical Steroids in Young Patients With Moderate Atopic Dermatitis A Randomized Clinical Trial. JAMA Dermatol. 2018;154(1):37-43. doi:10.1001/jamadermatol.2017.3647
Sublingual Allergy Treatment: What is it?
Using small doses of allergen to reduce allergy
Sublingual Immunotherapy (SLIT for short) is recognized by the World Health Organization as an effective treatment for people with allergies to a varieties of molds, grass pollens, dust, animal hairs/danders, ragweed, and certain mites/bugs. Subcutaneous therapy (or SCIT for short) is also widely used as a form of injection therapy to lower the allergic response. SLIT is more user friendly for those who have issues taking needles, or for small children. The specific allergen is diluted in a 1:100 or 1:1000 ratio. This is then administered under the tongue in a squirt pump bottle. You hold the solution in your mouth for two minutes and then swallow.
Research shows IgE mediated allergy such as seasonal inhalants and asthma reactions have favourable responses to treatment, with up to a 70% reduction in symptoms. The better the outcome is directly related to how strict the subjects were with taking their daily dose of medicine.
How long will it take to work?
The course of treatment is one squirt a day, anywhere from 2-3 months to 1-3 years for severe or multiple allergies. SLIT has been shown to reduce the sensitization to new allergens and stop the progression of allergies relating to the nose, airways, and breathing. (1) A meta analysis study showed reduction in asthma symptoms and medication use in 441 subjects aged 3-18 years who had mite sensitivity. (2) Studies on birch pollen and grass pollen have showed favourable results as well. In adults with dust mite allergy, a 3-year duration of SLIT had a lasting effect of five years after therapy. (3)
Are there side effects?
Most adverse experiences are mild itching, swelling, or tingling of the mouth, and watery eyes which go away on their own. SLIT has a lower adverse experience profile than its cousin, the injectable SCIT therapy. Currently food allergens are not treated in this way due to high risk of anaphylaxis, i.e. peanut allergy, cows milk, egg, shellfish, or celiac disease are not able to be treated using SLIT. There are experimental research concerning foods, therefore in the future we may be able to desensitize people using similar methods.
The absolute contraindication for SLIT is uncontrolled allergic asthma.
1) Passalacqua G. Specific immunotherapy: beyond the clinical scores. Ann Allergy Asthma Immunol. 2011 Nov; 107(5):401-6.
2) Penagos M, et al. Metaanalysis of the efficacy of sublingual immunotherapy in the treatment of allergic asthma in pediatric patients, 3 to 18 years of age. Chest. 2008 Mar; 133(3):599-609.
3) Marogna M, Spadolini I, Massolo A, Canonica GW, Passalacqua G. Long-lasting effects of sublingual immunotherapy according to its duration: a 15-year prospective study. J Allergy Clin Immunol. 2010 Nov; 126(5):969-75.
4) Pajno GB, Bernardini R, Peroni D, et al. Clinical practice recommendations for allergen-specific immunotherapy in children: the Italian consensus report. Italian Journal of Pediatrics. 2017;43:13. doi:10.1186/s13052-016-0315-y.