Allergy, Eczema, Asthma | May 7, 2014 | Author: The Super Pharmacist
Allergies can manifest in various forms. Skin allergies may present as hives or eczema. Allergic rhinitis occurs when the nose is involved. People may suffer from food allergies where certain foods can lead to bloating, vomiting and diarrhea. Allergic manifestations in the lungs present as the well-known condition called asthma. Individuals may be allergic to insect venom1 or even medications. When any form of an allergic reaction becomes especially severe and potentially life-threatening, it is called an anaphylactic reaction. Allergies are common and distressing. The incidence is on the rise worldwide and this is somehow attributed to industrialisation and improved standards of living. Considering the high toll allergy takes on healthcare spending, productivity factors and, for that matter, precious lives; there is a worldwide effort to develop better and more effective treatments.
Understanding the allergic cascade is important in providing us with knowledge of opportunities along the cascade where interventions (such as medications) can block, prevent or at least reduce the signs and symptoms of an allergy. Various groups of available medications do this and upcoming new medications and treatment modalities promise to make a difference in the lives of patients with allergy. The allergic cascade starts with exposure to an allergen. Avoiding the allergen may be all that is necessary to reduce the effects of an allergy. This may be impractical in circumstances where the allergen is as ubiquitous as dust, smoke or pollen in the air, or unidentifiable. However it is an effective strategy for well-defined food allergies. A person allergic to animal dander may choose to live without pets. Even for the common allergens in the air, steps can be taken to improve outcome, such as avoiding travel to pollen-rich areas in spring.
Steroids (corticosteroids) have a generalised suppressant effect on the immune system. Since allergies are due to a hypersensitive and overly aggressive immune system, steroids have been the mainstay of allergy treatments for quite some time. Different formulations are available for different allergic manifestations. Steroid nasal sprays2 for allergic rhinitis, eye drops for allergic conjunctivitis, topical creams and lotions for eczema and inhaled corticosteroids for asthma. When any form of allergy is increasingly resistant to treatment, a course of oral or injectable steroids will remarkably improve most signs and symptoms. We know that chemical mediators released by mast cells and basophils are responsible for the manifestations of allergy. Drugs that stop these cells from pouring out these harmful contents and ‘stabilize’ their membranes are called ‘mast cell stabilizers’. They have been helpful to many allergic patients and include compounds such as cromolyn (used in inhalers and eye drop preparations) and nedocromil (used in inhalers). Among the released mediators, histamine is especially important and behind many of the severe effects. Drugs that block histamine receptors and prevent histamine binding are cornerstones of allergy treatment and prevention in most cases. Such drugs are called antihistamines and include a long list of compounds, including loratadine3, cetirizine, fexofenadine.
Asthmatic patients would benefit from steroids, antihistamines and mast cell stabilizers. They would also find immediate relief with the use of inhaled short acting beta-2 agonists such as salbutamol (Ventolin) and to some extent with inhaled anticholinergics such as ipratropium. Long acting beta-2 agonists such as salmeterol are effective in preventing recurrence of attacks for up to 24 hours. Nasal decongestants can relieve nasal obstruction and stuffiness in allergic rhinitis. Such decongestants can be in the form of nasal sprays (xylometazoline) or oral tablets (pseudoephedrine).
In any form of allergy, a severe manifestation could be an anaphylactic shock which would require adrenaline shots. Auto-injector devices containing adrenaline include EpiPen and Anapen. These could be lifesaving and should always be kept with a patient with a history of previous anaphylactic reactions.
One way of ‘desensitising’ the allergic person can be to expose the immune system to adjusted doses of the allergen over months to years and hope that the immune system will learn to tolerate the allergen and stop overreacting to it. This is the basis of immunotherapy4 (allergy shots) which can be particularly successful in treating certain candidates.
Latest developments in allergy management are interesting. They include novel devices, alternative approaches, and new drugs that hope to make a huge impact. Novel devices include dehumidifiers, based on the principle that household allergens such as molds and mites need moisture to grow. Gadgets like nasal filters vow to capture allergens before they enter respiratory passages. Alternative medicine presents its own array of treatments and cures. Chinese herbal formulae aim to desensitize the gut of multiple food allergies. Some intestinal worms initially thought to be harmful parasites are now being considered symbionts. So are some bacteria. These new trends stem from research approval of the hygiene hypothesis, which indicates that absence of such agents can adjust the TH1/ TH2 (specialised white blood cells) balance.
Most significantly new therapeutic agents have made an entrance and some are on the horizon. Leukotrienes (chemical messengers) released by the immune cells can be blocked by the antileukotrienes, montelukast3 (already used orally for asthma) and zafirlukast, before they can enhance the allergic response. The IgE antibody is central to the pathogenesis of allergic reactions. If we had a drug that targeted this very IgE and blocked its effects, we could remarkably improve allergy outcomes. Omalizumab5 is a drug that does just that. It is an antibody itself, directed against the IgE antibody, which it binds to and neutralizes, thereby disintegrating the allergic cascade and greatly benefitting the allergic person. Omalizumab is a ray of hope for asthmatics who are not responding to steroids. It has also shown potential in the treatment of other forms of allergies including food allergies. The advantages this drug can offer are being evaluated through numerous ongoing clinical trials.
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2. Nielsen LP, Dahl R. Comparison of intranasal corticosteroids and antihistamines in allergic rhinitis. Am J Respir Med. 2003;2:55–65.
3. Nayak AS, Philip G, Lu S, et al. Efficacy and tolerability of montelukast alone or in combination with loratadine in seasonal allergic rhinitis: a multicenter, randomized, double blind, placebo controlled trial performed in the fall. Ann Allergy Asthma Immunol. 2002;88(6):592–600. doi: 10.1016/S1081-1206(10)61891-1.
4. Incorvaia C, Mauro M, Ridolo E, et al. Patient’s compliance with allergen immunotherapy. Patient Prefer Adherence. 2008;2:247–251.
5. Thomson NC, Chaudhuri R. Omalizumab: clinical use for the management of asthma. Clin Med Insights Circ Respir Pulm Med. 2012;6:27–40.