Food Allergy – Skin Symptoms, Most Common Allergens. Studies on Food Allergies

Based on established medical criteria, **immunologically mediated adverse food hypersensitivity** represents a spectrum of recurrent adverse reactions that emerge in genetically or environmentally predisposed individuals following exposure to specific food components—even in trace quantities—without eliciting any symptoms in non-susceptible persons [1]. Epidemiological evidence suggests that this condition affects **approximately 1.2% to 10% of the global population**, translating to an estimated **250 to 550 million cases** worldwide. While the highest prevalence is documented among **infants and young children**, the disorder may **develop at any life stage**, including adolescence, adulthood, and late adulthood. The underlying pathophysiological mechanism involves an **aberrant immune response**, specifically the production of **allergen-specific immunoglobulin E (IgE) antibodies** targeted against particular food antigens. The IgE–allergen complexes subsequently trigger **mast cells and basophils**, prompting the release of **pro-inflammatory mediators** (e.g., histamine, leukotrienes, prostaglandins), which are responsible for the **diverse clinical manifestations**. These may include **gastrointestinal symptoms** (e.g., diarrhea, vomiting, abdominal pain), **cutaneous reactions** (urticaria, angioedema, atopic dermatitis), **respiratory disturbances** (asthma, rhinitis, bronchospasm), and **systemic responses** such as anaphylactic shock. Key **risk factors** associated with the development of this condition include: **genetic predisposition** (e.g., familial history of allergies), **intestinal mucosal barrier dysfunction**, **exposure to certain pharmaceutical agents** (e.g., acetylsalicylic acid, angiotensin-converting enzyme inhibitors, beta-blockers), and **food additives** (preservatives, artificial colorants, heavy metals, emulsifiers) [2, 3].

Cutaneous symptoms associated with food allergies may affect up to half of diagnosed patients. The most prevalent dermatological manifestations include atopic dermatitis (AD), diverse rashes, contact eczema, erythematous redness, persistent pruritus, and acute urticaria. In infants and young children, atopic dermatitis is frequently linked to the ingestion of cow’s milk proteins and may occur regardless of feeding method—whether breastfed or formula-fed. In the youngest patients, lesions are primarily localized to the cheeks, auricular regions, and extensor surfaces of the limbs, whereas in older children, changes predominate in the antecubital and popliteal fossae, palms, and exposed areas of the body. The skin in these regions is characterized by excessive dryness, often accompanied by intense itching. Atopic dermatitis may also arise as a reaction to inhalant or food allergens, manifesting as widespread erythema, xerosis, and relentless pruritus. In advanced cases, desquamation of the epidermis occurs, and during acute phases, generalized redness (erythroderma) may develop. Urticaria, another hallmark of food allergy, can be triggered by contact allergens, inhalants, medications, or specific dietary components. In adults, peanuts, hazelnuts, fish, and shellfish are the most common culprits, whereas in children, hen’s eggs, cow’s milk, wheat, soy, and nuts predominate. Urticaria is typified by pruritic wheals that resolve spontaneously without leaving permanent marks on the skin.

Immunologically mediated adverse reactions to dietary components exhibit a higher prevalence among pediatric populations compared to adults, according to epidemiological data. The primary culprits responsible for the majority of food hypersensitivity cases comprise eight distinct food categories, which may be subdivided into four animal-derived sources—including bovine milk proteins, hen’s eggs, finfish, and marine invertebrates such as crustaceans and mollusks—and four plant-derived sources, namely tree nuts, groundnuts (botanically classified as legumes), soybeans, and wheat grains, as systematically categorized in reference [6]. These allergenic substances consist of proteinaceous compounds capable of eliciting IgE-mediated immune responses, wherein cow’s milk allergy is predominantly driven by caseins and whey proteins (specifically alpha-lactalbumin and beta-lactoglobulin), while hen’s egg allergy involves as many as twenty-three distinct protein fractions, with ovomucoid, ovalbumin, and ovotransferrin (commonly referred to as conalbumin) representing the most clinically significant allergens. In contrast, hypersensitivity to fish and shellfish is primarily attributed to parvalbumins—a class of calcium-binding proteins uniquely expressed in the muscle tissue of these aquatic organisms—serving as the major immunogenic triggers.

The diagnostic process for food allergies represents a multifaceted, interdisciplinary endeavor that integrates data from clinical history, symptom observation, and specialized laboratory and immunological assessments. Given the absence of a single pathognomonic test capable of definitively confirming the diagnosis—and the highly variable clinical presentation, which may range from dermatological manifestations to gastrointestinal or respiratory disturbances—a comprehensive series of diagnostic steps is essential. Core components include: a thorough medical history evaluation (focusing on the nature, duration, and anatomical distribution of symptoms), a physical examination (assessing overall health status and organ system functionality), and allergo-immunological investigations, such as quantitative measurement of specific IgE antibodies in serum or skin prick testing using standardized food allergen extracts. It is critical to note that a positive skin test result does not constitute conclusive evidence of food allergy; verification via a controlled oral food challenge with the suspected allergen is mandatory. The gold standard in diagnosis remains the elimination-challenge test, which involves the temporary removal of the suspected allergenic food from the diet for 1–4 weeks, followed by a gradual, medically supervised reintroduction while monitoring for adverse reactions. Particular emphasis is placed on common triggers such as cow’s milk proteins, hen’s eggs, nuts, wheat, and fish, which are most frequently implicated in hypersensitivity reactions. Symptoms of food allergy may encompass cutaneous manifestations (e.g., atopic dermatitis, erythema, pruritus) as well as gastrointestinal or respiratory complaints. Definitive diagnostic confirmation requires correlation of serological test results, skin test outcomes, and clinical observations during the challenge phase.