A recent review article in Current Opinion in Immunology explores a comprehensive range of strategies to prevent chronic allergic diseases. These include primary, secondary, and tertiary prevention approaches aimed at addressing conditions like asthma, atopic dermatitis, allergic rhinitis, and food allergies.
Rising Global Prevalence of Allergic Diseases
Allergic diseases have become a significant global health concern, leading to increased morbidity and mortality. Conditions such as asthma and atopic dermatitis are particularly prevalent among children, with asthma alone responsible for 455,000 deaths globally in 2019, according to the World Health Organization.
Environmental factors, such as pollution, medications, and changes in gut microbiota, contribute to the onset of these conditions. The review explains how exposure to environmental allergens triggers immune responses that lead to allergic inflammation. Specifically, allergens activate immune cells, causing the production of allergen-specific IgE, which further fuels allergic reactions through the release of histamine and leukotrienes.
Primary Prevention: Preventing Allergic Sensitization
Primary prevention focuses on reducing the risk of allergen sensitization before it occurs.
Food Allergy
Early introduction of allergenic foods, such as peanuts and cow’s milk, is a key preventive measure. Evidence suggests that introducing complementary foods around six months of age and allergenic foods before 11 months can significantly lower the risk of food allergies. Notably, the Learning Early About Peanut (LEAP) trial showed that early peanut introduction reduced peanut allergy by 86% in high-risk children.
However, other preventive methods, such as dietary avoidance, probiotics, and vitamin supplements, show uncertain results, with limited evidence supporting their effectiveness.
Allergic Asthma
Primary prevention of allergic asthma primarily targets the prevention of IgE sensitization. Allergen immunotherapy, which has been used in children with asthma, shows some promise but has not been effective in preventing new sensitizations.
Additionally, the anti-IgE monoclonal antibody, omalizumab, has shown positive outcomes in reducing disease progression. Currently, the Preventing Asthma in High-risk Kids (PARK) trial is testing omalizumab in young children to determine its role in delaying asthma onset.
Atopic Dermatitis
For atopic dermatitis, prevention strategies include minimizing skin inflammation, fortifying the skin barrier, and avoiding allergen exposure. While the application of emollients is a common preventive method, evidence suggests that they do not significantly reduce eczema in high-risk populations. Some studies even indicate that emollients could increase the risk of food allergies due to the transfer of allergens through the skin.
Other promising strategies include maintaining a healthy diet during pregnancy to support gut microbiota, avoiding unnecessary antibiotics, and promoting exclusive breastfeeding for the first few months of life.
Secondary Prevention: Reducing Symptoms After Sensitization
Secondary prevention aims to alleviate symptoms in individuals already sensitized to allergens.
Food Allergy
Oral immunotherapy, which involves gradually increasing allergen exposure, has shown promising results in improving tolerance to allergens like peanuts and cow’s milk. This therapy has proven effective in children without triggering serious adverse events. FDA-approved oral immunotherapy for peanut allergies is also available for children aged 4 to 17.
Allergic Asthma
For allergic asthma, allergen immunotherapy is the most effective secondary prevention method. Studies suggest that subcutaneous and sublingual immunotherapy can reduce the risk of asthma in individuals with allergic rhinitis.
Atopic Dermatitis
Secondary prevention for atopic dermatitis focuses on protecting the skin barrier by eliminating irritants and reducing stress and sweating. Some smaller trials have suggested that emollients might offer some benefits, though overall results remain inconsistent.
Tertiary Prevention: Managing Disease Exacerbations
Tertiary prevention focuses on managing and reducing the severity of allergic reactions in individuals who have already developed the disease.
Food Allergy
In tertiary prevention, the goal is to prevent severe allergic reactions, such as anaphylaxis. Allergen immunotherapy, including oral and sublingual methods, shows promise in increasing tolerance levels, although these treatments carry risks of adverse reactions. Omalizumab has demonstrated positive results in raising the threshold for anaphylactic reactions, with a recent trial showing that 67% of children receiving omalizumab could tolerate 600 mg of peanut protein compared to just 7% in the placebo group.
The “food ladder” approach, which introduces baked versions of allergens like milk and eggs, has also shown promise in safely building tolerance in allergic children.
Allergic Asthma
Tertiary prevention for allergic asthma focuses on preventing exacerbations and maintaining symptom relief after treatment. Omalizumab and other biologics, such as mepolizumab and dupilumab, have proven effective in reducing asthma flare-ups and hospitalizations.
Atopic Dermatitis
In managing atopic dermatitis, topical corticosteroids and biologic treatments like dupilumab and omalizumab have shown positive outcomes in reducing disease severity. However, long-term effectiveness and cost-efficiency remain under investigation.
Conclusion
This review underscores the complexity of allergic diseases and highlights the importance of a layered approach to prevention. Early allergen introduction, targeted immunotherapy, and biologic treatments, such as omalizumab, offer promising results in altering the disease course. However, some commonly used methods, such as emollients for eczema prevention, lack consistent evidence and may carry potential risks.
Ongoing research into gene editing and combination therapies may provide new avenues for more effective allergy prevention and treatment in the future.
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