Basics
Allergic diseases include atopic dermatitis, food allergy, asthma, and allergic rhinitis. Atopic or allergic diseases are becoming more and more prevalent in the population.
- Food allergy in its most severe form may manifest as anaphylaxis.
- The conditions may present in a variety of ways as described below.
Description
- Atopic dermatitis
- Atopic dermatitis (or eczema) is characterized by chronic, relapsing, pruritic inflamed skin which is often erythematous, xerotic, and/or excoriated.
- Atopic dermatitis may occur in isolation without other atopic diseases.
- Atopic dermatitis may also be the beginning of the "atopic march" in which atopic dermatitis precedes the onset of other atopic conditions which may include food allergy, asthma, and allergic rhinitis.
- Urticaria
- Refers to hives or the erythematous wheals that occur when histamine is released from mast cells
- May be caused by a number of triggers
- Viral infection is the most common cause of urticaria in children.
- The allergic child may develop urticaria when an antigen such as a food or animal dander causes IgE-mediated release of mast cell mediators.
- Food allergy
- Presents with an IgE-mediated reaction after exposure to a food to which the child is sensitized
- Reactions may present with any number of symptoms, including urticaria, lip or tongue swelling, closing of the throat, wheezing, shortness of breath, repeated vomiting after allergen ingestion, diarrhea, or any combination of the above.
- The most common food allergens include cow's milk, egg white, peanut, tree nuts, wheat, soy, fish, and shellfish.
- Food allergy should be distinguished from food intolerance which has a nonimmunologic basis and does not carry a risk of anaphylaxis.
- Asthma
- An obstructive airway disease characterized by recurrent wheezing, bronchoconstriction, increased mucous production, and airway inflammation
- Asthma is one of many potential causes of wheezing in children.
- Wheezing with RSV and human rhinovirus infection are risk factors for the development of asthma.
- Allergic rhinitis
- A condition in which children are sensitized to perennial allergens, seasonal allergens, or both
- Perennial allergens include dust mite, molds, cockroach, and animal dander.
- Seasonal allergens include tree pollens, grass pollens, or ragweed.
- Rhinitis symptoms may include watery eyes, itchy eyes, rhinorrhea, nasal discharge, itchy nose, postnasal drip, headache, sinus pressure, nasal obstruction, mouth breathing, or snoring.
- Symptoms may be seasonal, year-round, or triggered by exposure to specific allergens (such as cats or dogs).
Risk Factors
Genetics
- Children who do not have a family history of atopy have approximately 25% chance of being atopic.
- For children with at least one parent who is atopic, the risk of atopy approximately doubles compared to the general population.
Pathophysiology
Most of these allergic conditions are IgE mediated, and all of them result from a complex interaction between multiple genetic and environmental factors.
Diagnosis
A thorough history and physical examination are the keys to diagnosing the allergic child.
History
- History should elicit signs and symptoms of allergic diseases while at the same time exploring other potential etiologies for the child's symptoms.
- The allergic child should have symptoms of atopic dermatitis, urticaria, wheezing, reactions to foods, or symptoms of rhinitis such as sneezing, itchy eyes, watery eyes, itchy nose, runny nose, or itchy throat.
- The practitioner should also review the family history as atopic disease often runs in families.
Physical Exam
A complete physical exam is essential to rule out systemic diseases that can mimic allergic disease.
- Finding: Ocular signs may include the following:
- Dark circles under the eyes or the so-called "allergic shiners" which result from venous stasis secondary to passive congestion in the nose, impeding venous return to the vessels under the eyes
- Cobblestoning of the conjunctiva
- Erythematous injection of the conjunctiva
- Dennie-Morgan lines or infraorbital folds associated with suborbital edema secondary to chronic inflammation from atopic dermatitis
- Clear stringy ocular discharge
- Finding: Nasal allergic signs may include the following:
- Pale edematous nasal mucosa
- Clear nasal discharge with or without occlusion
- Nasal crease across the bridge of nose secondary to repeated upward rubbing of the nose from "the allergic salute"
- Nasal polyps may be present, although they are much more common in adults and should prompt consideration of diseases such as cystic fibrosis when seen in children.
- Finding: Ear allergic signs may include the following:
- Fluid in the middle ear or retracted tympanic membranes
- Eustachian tube dysfunction associated with allergic inflammation
- Finding: Throat allergic signs may include the following:
- Cobblestoning of the posterior pharynx secondary to submucosal lymphoid hyperplasia
- Finding: Lung allergic signs may include the following:
- Wheezes, rhonchi, decreased air entry, prolonged expiration, and chronic obstruction secondary to allergic responses
- Finding: Skin allergic signs may include the following:
- Eczema, hives, angioedema, and dermatographism
Differential Diagnosis
The differential for allergic diseases is extensive and should focus on considering other etiologies for the symptoms.
- Ear/nose symptoms
- Eye findings may be caused by physical or chemical irritants or by viral or bacterial infection.
- Allergic rhinitis symptoms may resemble upper respiratory infections, sinusitis, nasal foreign bodies, or nonallergic rhinitis.
- A number of medications can also lead to rhinitis medicamentosa, or symptoms of nasal congestion due to medication use.
- Systemic diseases such as cystic fibrosis, immotile cilia syndrome, Kartagener syndrome, or immunodeficiencies may present with recurrent nasal symptoms and/or with lung symptoms.
- Lung symptoms may be caused by physical or chemical irritants including tobacco smoke, environmental pollution, and inhalants.
- Chest symptoms
- Lung symptoms may also result from gastroesophageal reflux leading to (nocturnal) cough.
- Foreign body aspiration may produce lung symptoms and auscultatory signs, although typically, foreign bodies create more focal lung findings.
- Anatomic defects in the airway may also result in symptoms that are similar to allergic symptoms.
- Skin symptoms
- Skin findings may be caused by a number of etiologies including irritant dermatitis, viral exanthems, autoimmune disorders, bacterial, fungal, or parasitic infections.
- Multisystem
- Anaphylaxis may sometimes be confused with angioedema, vocal cord dysfunction, globus hystericus, or with other causes of shock (sepsis, hypovolemia, cardiogenic).
- Food allergy may sometimes be confused with food intolerance, but food intolerances present with abdominal discomfort, bloating, flatulence, or nonspecific malaise, whereas food allergy presents with true IgE-mediated reactions.
Diagnostic Tests & Interpretation
The diagnosis of allergic diseases can be strongly suggested based on history and physical alone. Specific tests can be done by a specialist in allergy and immunology in order to be properly interpreted. Often, initial therapy can be initiated without definitive tests.
Once the allergic child is referred to the allergist, testing may include the following:
- Immediate hypersensitivity testing
- Skin prick tests to suspected allergens based on history may demonstrate IgE sensitization if positive.
- Intradermal skin tests for patients who have a negative skin prick test and a suspicious history pose a greater risk of systemic reactions but can be done for environmental allergens, not for foods.
- Blood-specific IgE testing
- ImmunoCAP tests measure free serum IgE to a specific antigen to which a particular patient may be sensitized.
- Although panels are available, these tests are best done for targeted potential allergens that are suggested by the history and should be interpreted by an allergist with experience in interpreting and guiding therapy.
- Incorrect use or interpretation of ImmunoCAP testing may result in inappropriate dietary restrictions, nutritional deficits, and undue anxiety.
- ImmunoCAP levels may be trended over time to help monitor for the development of tolerance.
- Eosinophilia
- Eosinophils in the blood (on a CBC) or in respiratory secretions or nasal samples may be indicative of an allergic diathesis.
- Pulmonary function tests (PFTs)
- PFTs or spirometry should be obtained on asthmatic children or in children with respiratory allergic histories to evaluate for obstructive diseases.
Treatment
General Measures
- The main principle of therapy for allergic diseases is avoidance of allergic triggers.
- For atopic dermatitis, general treatment measures include measures to help lock moisture into skin, treat inflammation when present, control pruritus, minimize skin irritants, and treat infection when present.
- For food allergy, the most important therapeutic measure is strict avoidance of the food that causes the allergy in order to prevent an allergic reaction.
- Children at risk for a reaction to a food allergen should be prescribed an epinephrine autoinjector to use in the event of systemic symptoms or anaphylaxis.
- An emergency action plan should be provided, reviewing the signs and symptoms of a reaction and the doses and medications that should be used in the event that an accidental ingestion occurs.
- For allergic rhinitis, systemic antihistamines may be helpful in controlling symptoms. Many patients also benefit from intranasal corticosteroids when indicated.
- Specific environmental control measures may be indicated based on specific skin testing results.
- Pets should be kept out of the bedroom if a child has allergic stigmata due to animal dander.
- To minimize exposure to dust mite allergen, the bedding should be encased in dust mite encasements and washed in hot water at least once every 2 weeks.
- Immunotherapy may be indicated for patients with allergic rhinitis or venom allergy.
- For patients with asthma, treatment should follow the latest National Heart, Lung and Blood Institute (NHLBI) of the National Institutes of Health (NIH) asthma guidelines with consideration to the child's symptomatology, impairment, and risk. Therapies may include use of rescue inhalers, controller medications such as inhaled corticosteroids, leukotriene antagonists, and others (see Appendix, Figure 5). Control of comorbidities such as allergic rhinitis and GERD are also important therapeutic steps.
Issues for Referral
- Any child with allergic symptoms may benefit from referral to an allergist-immunologist.
- A patient failing medical management of upper respiratory or ocular allergies with routine antihistamine/decongestant medications may be referred to an allergist who can help identify triggers contributing to the problem.
- Poorly controlled asthma not responding to intermittent inhaled β-agonists or an asthmatic child who is symptomatic between exacerbations or has an atypical pattern of exacerbations should be referred.
- Asthma patients with frequent hospitalizations or steroid dependence should be referred.
- Patients who are absent from school frequently because of allergic or asthmatic symptoms should be referred.
- Patients with food allergy, drug allergy, latex allergy, or difficult-to-manage atopic dermatitis should also be referred to an allergist.
Ongoing Care
Prognosis
- In general, environmental allergies that cause rhinitis and asthma persist into adulthood.
- About 50% of milk-allergic children may outgrow their allergy by school age and about 80% by age 16 years. Those who tolerate baked milk seem to have a higher likelihood of outgrowing the allergy.
- About 60-80% of egg-allergic children may outgrow their egg allergy. Children who tolerate baked egg seem more likely to outgrow the allergy.
- Children may occasionally outgrow peanut, tree nut, or shellfish allergy.
- Allergic diseases may have a significant impact on the patient and family's quality of life and may lead to issues with anxiety and mental health.
Additional Reading
- Adkinson NF, Bochner BS, Busse WW, et al. Middleton's Allergy Principles and Practice. 7th ed. Philadelphia, PA: Mosby; 2009.
- Hatzler L, Hofmaier S, Papadopoulos NG. Allergic airway diseases in childhood-marching from epidemiology to novel concepts of prevention. Pediatr Allergy Immunol. 2012;23(7):616-622. [View Abstract]
- Langley EW, Gigante J. Anaphylaxis, urticaria and angioedema. Pediatr Rev. 2013;34(6):247-257. [View Abstract]
- Papadopoulos NG, Arakawa H, Carlsen KH, et al. International consensus on (ICON) pediatric asthma. Allergy. 2012;67(8):976-997. [View Abstract]
- Wood RA, Sicherer SH, Vickery BP, et al. The natural history of milk allergy in an observational cohort. J Allergy Clin Immunol. 2013;131(3):805-812. [View Abstract]
Codes
ICD09
- 691.8 Other atopic dermatitis and related conditions
- 693.1 Dermatitis due to food taken internally
- 493.00 Extrinsic asthma, unspecified
- 477.0 Allergic rhinitis due to pollen
- 995.0 Other anaphylactic reaction
- 995.3 Allergy, unspecified, not elsewhere classified
- 692.3 Contact dermatitis and other eczema due to drugs and medicines in contact with skin
ICD10
- L20.9 Atopic dermatitis, unspecified
- L27.2 Dermatitis due to ingested food
- J45.909 Unspecified asthma, uncomplicated
- J30.1 Allergic rhinitis due to pollen
- T78.2XXA Anaphylactic shock, unspecified, initial encounter
SNOMED
- 24079001 Atopic dermatitis (disorder)
- 414285001 food allergy (disorder)
- 389145006 allergic asthma (disorder)
- 61582004 Allergic rhinitis (disorder)
- 39579001 Anaphylaxis (disorder)
FAQ
- Q: Do children outgrow allergies?
- A: In general, environmental allergies that cause rhinitis and asthma persist into adulthood. However, most children outgrow food allergies to milk, egg, soy, and wheat. Children may occasionally outgrow peanut, tree nut, or shellfish allergies.
- Q: If a parent is allergic to a specific allergen, can the child inherit this allergy?
- A: Children inherit the tendency to be allergic, but they do not inherit specific allergies.
- Q: How can allergies be prevented?
- A: Allergy prevention is currently not possible, but research in this field is ongoing.