If you think your allergies are getting worse, it is entirely possible, said Dr. Bridget Hathaway, MD, Assistant Professor in the Department of Otolaryngology and Director of Allergy for the Department in the Eye & Ear Foundation’s March 22 webinar entitled, “Spring Fling – An Update on the Evaluation and Treatment of Allergies.”
One of the things fueling allergy severity is climate change. Other factors include:
- Warmer winters –> plants and trees bloom earlier and for a longer period of time
- Increasing CO2 levels enhance photosynthesis–>plants produce more pollen
- Particulate matter in pollution + pollen = stronger immune response
Demographics of Allergy
Allergies are incredibly common, Dr. Hathaway said. If you do not have them, you most likely know someone close to you who does.
- Roughly 7.8% of adults in US have hay fever
- 9% of children reported hay fever in 12 months (2012)
- 11 million visits to physician offices resulted in diagnosis of allergic rhinitis (2010)
- 8% of children in US have a food allergy
- Peanuts, milk, shellfish
Public Health Paradox
In 1989, epidemiologist David Strachan proposed the theory that a reduced exposure to dirt could render a person prone to allergy. This led to the popular “hygiene hypothesis.”
A 2011 article in Nature has the following quote: “With clean drinking water, sanitation, vaccinations, and advances in medicine, many diseases were on the wane. So why was it that allergic diseases were becoming more prevalent, particularly in industrialized and urban parts of the world?”
Some of the reasons listed:
- Less exposure to infectious agents during childhood
- Antimicrobial soaps, antibiotics, cleanliness
- Number of older siblings
- Daycare in first 6 months –> lower risk of asthma and eczema
- Children who grow up on farms are 3x less likely to have allergies
- Protective effect of unpasteurized cow’s milk
- Eradication of parasitic infections –> loss of protection from allergy
Immune System
It all comes down to our immune system, Dr. Hathaway said. There are two main pathways in terms of responding to various threats: Phenotypes Th1 and Th2, which respond differently.
Factors favoring Th1 are the presence of older siblings, early exposure to daycare, tuberculosis, measles, or hepatitis A infection, and a rural environment. These lead to protective immunity.
Factors favoring Th2: widespread use of antibiotics, Western lifestyle, urban environment, diet, and sensitization to house-dust mites and cockroaches. These lead to allergic diseases, including asthma.
Allergy Mediated Diseases
- Allergic rhinitis
- Conjunctivitis
- Oral allergy syndrome
- Asthma
- Eosinophilic esophagitis
- Atopic dermatitis (eczema)
- Food allergy
All of these have one thing in common – from a part of the body that is exposed to the outside world.
Allergy Symptoms
- Rhinorrhea (thin, mostly clear nasal discharge)
- Cough
- PND (post nasal drip)
- Epiphora (excessive watering of the eye)
- Hoarseness
- Facial pressure
- Sleep disturbance
- Fatigue
Causes of Rhinitis
Allergy
- Seasonal
- Perennial
- Intermittent/persistent
Other causes:
- Vasomotor
- Irritant induced
- Occupational
- Tobacco
- Infectious
- Drug related
- Hormonal
- Gustatory
Histamine
- Primary mediator from mast cells/basophils of early phase of allergic response
- Starts at 5 minutes and peaks at 30 minutes
- Pruritis (itchy skin)
- Increased vascular permeability
- Increase HR and force of contraction
- Increase goblet cell and bronchial gland secretion
- Smooth muscle contraction in bronchial tree
Antigen
- Substance that prompts the innate immune response
- Contains a T-cell and B-cell epitope
- Epitope
- Part of a macromolecule that is recognized by the immune system
- Three-dimensional surface features of an antigen molecule
- Fits precisely and binds to antibody
- May cross react with multiple antibodies
- An antigen may have many epitopes
Tree Pollen
- Spring
- Angiosperms (covered seeds, flowering)->more allergenic
- Oak, birch, maple, olive/ash
- Cross reactivity within subfamilies
- Test and treat for regionally important ones
- Gymnosperms (“naked seeds”)
- Cyprus, cedar, redwoods
Grass Pollen
- Summer
- Among most potent allergens: many standardized Ags
- 3 main allergenic subfamilies:
- Pooidae – Timothy
- Chloridoideae – Bermuda
- Panicoideae – Bahia and Johnson
Weed Pollen
- Fall
- Ragweed, mugwort, goldenrod, lambs quarters, pigweed
Pet Allergens
- Dander (shedding/dead skin), saliva, tears and urine are allergenic
- Cat: major Ag determinant fel d 1 very potent/sticky/widely distributed
- Always test cat
- Small Ag 5-10 microns–>rhinoconjunctivitis, asthma
- Dog can f1 not as potent as cat/rodent
- If history of exposure, may need to test rabbit, rodent, horse, livestock
Dust Mite
- Year round
- Indoors
- Small (10 micron) very allergenic–> rhinoconjunctivitis, asthma
- D. farina, D. pteronyssinus
- Sublingual tablet available
- Weight of a 2-year-old pillow could be 33% dust mites!
Allergens
- Roach dander
- Indoors, year-round, high humidity, urban
- Molds
- Airborne spores; humid areas in fall, winter, indoors
- >1 million species
- Variable antigenic determinants that can stimulate type I and cell-mediated immunity
Allergy Treatment
- Avoidance/environmental controls
- Medication
- Immunotherapy
Environmental Controls
- Minimize carpet, stuffed animals, drapery
- Mattress covers and pillow covers
- Wash bedding in hot water
- Change pillowcase frequently
- Air purifiers/HEPA filters – has to be powerful enough to fit the space, look for specifications
- Dehumidifiers
- N-95 mask
Medications
There is an overwhelming number of options:
- Steroids
- Antihistamines
- Decongestants
- Mucolytics
- Anticholinergics
- Anti-leukotrienes
- Mast cell stabilizers
Steroids
- Downregulates inflammatory responses by binding to intracellular glucocorticoid receptor
- Oral steroids can be helpful for severe, acute allergy flare or anaphylaxis
Intranasal steroids
- Nasal and eye symptoms
- 5-7 days to reach full efficacy
- More effective with consistent use
- Low systemic absorption
- Caution: glaucoma or cataracts
- Approved for use in pregnancy
- Pretty safe, low risk
Antihistamines
Antihistamines affect early and late phase allergic reactions. There are adverse effects, like sedation, decreased cognitive performance, and motor coordination.
- Relatively rapid onset
- Helpful for nasal, eye, and skin symptoms
- Can be used as needed
- Widely available
- Safe
Decongestants
Topical decongestants
- Oxymetazoline, phenylephrine
- Onset of action<5 minutes
- Duration>6 hours
- Risk tachyphylaxis
- Rhinitis medicamentosa
Oral decongestants
- Pseudoephedrine
- Vasoconstriction->decreased blood flow->decreased edema
- Interactions – best to check with your primary care physician if you have one of the following conditions
- High blood pressure
- Glaucoma
- MAO inhibitors
- Urinary retention
- Stroke
Allergy Testing
- Sinonasal symptoms not explained by infection, structural issues (DNS), irritants
- Provide objective measure of severity of sensitivity
- Determine if there is an indication and safe starting dose for immunotherapy
- Not necessary when history is consistent with allergy and symptoms are managed with environmental controls +/- medication
Allergy Testing Techniques
- Prick testing
- Intradermal testing
- Single intradermal test
- Intradermal Dilutional testing (IDT)
- Modified Quantitative Testing (MQT)
- In vitro specific IgE testing
- Radioallergosorbent test (RAST), enzyme linkage (ELISA), fluorescence (FEIA)
Why Skin Testing?
- Mast cells reside in subepithelial layer of skin
- Skin is accessible
- Allergen + sensitized mast cell–>allergic reaction with release of chemical mediators
- Indirect measure of cutaneous mast cell reactivity due to presence of specific IgE
- *History must be correlated with skin testing results!
Intradermal Dilutional Testing
- Inject .01-.05 ml injected intradermally to create a 4 mm wheal which grows to 5 mm by osmosis
- Positive wheal grows at least 2 mm larger than the wheal initially created
- Positive and negative controls (glycerin and histamine)
Prick Testing
- Use concentrate
- Antigen placed on skin and skin “pricked” with a sharp device
- Read at peak size (15-20 mins)
- Measure wheal
- Positive and negative controls
- 3 mm wheal is positive
Antihistamines must be stopped five days prior to skin testing, or they will interfere with the results.
Contraindications to Skin Testing
- Poorly controlled asthma
- Nonselective beta blockers
- Recent antihistamine use
- Dermatographism – someone whose skin reacts to anything
Blood Test: In Vitro Specific IgE Testing
- Fixed allergen – patient’s serum IgE – anti IgG sandwich
- Measurement of Ige by
- Radioallergosorbant test (RAST)
- Enzyme linkage (ELISA)
Pros of blood testing:
- Safety
- No risk of local or systemic reactions
- No need to stop antihistamine
- Can be used with dermatographism
- Can obtain starting endpoints for immunotherapy
Cons:
- Results not immediate
- Older assays lower sensitivity compared with skin testing
- Cost
- Possibly longer escalation phase in SCIT
Principles of Immunotherapy
- Induce immunologic response to a specific antigen by
- Altering T cell response
- Restoring Th1/Th2 balance
- Production of specific IgG (blocking antibodies)
Immunotherapy
- Intentional exposure to specific antigen(s)
- Regular dosing
- Progressive escalation of dosage
- Avoid unacceptable local and systemic reactions
Routes for Immunotherapy
- Subcutaneous
- Sublingual
- Not FDA approved
- FDA approved
- Dust mites (Odactra)
- Grass pollen (Oralair or Grastek)
- Short ragweed (Ragwitek)
Bottom Line
The bad news is allergies can start anytime because the immune system is always changing. The good news is that effective treatments are available.