What you carry at this position in your DNA and what research says about it.
Asthma and Eczema Risk: 10/10 evidence, 73 publications.
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Sample genotype (not yours): A/A
Higher Risk of Asthma and Eczema
Two copies of the A allele are linked to an overactive allergic immune response. This increases susceptibility to asthma, eczema, and hay fever while keeping psoriasis risk low.
What this genotype means: Increased susceptibility to asthma and breathing difficulties; Higher likelihood of developing atopic eczema and hay fever; Lower risk of developing autoimmune psoriasis.
Sample genotype (not yours): A/G
Slightly Higher Risk of Allergies and Asthma
Carrying one copy of each allele creates a balanced but slightly elevated risk profile. You have a moderate susceptibility to both allergic conditions and psoriasis.
What this genotype means: Mildly elevated risk of asthma and seasonal allergies; Slightly increased susceptibility to dry, itchy eczema; Slightly higher risk of psoriasis compared to A/A homozygotes.
Sample genotype (not yours): G/G
Lower Allergy Risk but Higher Psoriasis Risk
Two copies of the G allele protect against asthma and eczema by dampening allergic pathways. However, this same immune shift increases the risk of psoriasis.
What this genotype means: Significantly lower risk of developing asthma and eczema; Increased susceptibility to psoriasis and psoriatic skin plaques; Potentially better response to certain asthma controller medications.
Gene function and biological role
Gene Function: The IL13 gene encodes interleukin 13, an immunoregulatory cytokine primarily secreted by activated T-helper type 2 (Th2) cells [1]. This cytokine plays a central role in regulating allergic inflammation and stimulating B cells to produce immunoglobulin E (IgE) antibodies [1] [2]. Elevated levels of interleukin 13 drive the inflammatory cascade that underlies airway hyperresponsiveness and skin barrier disruption [2] [3]. Consequently, genetic variations in this gene are heavily implicated in susceptibility to various atopic and inflammatory conditions [3] [4].
Variant Impact: The rs20541 variant is a missense mutation in exon 4 of the IL13 gene, resulting in a change from glutamine to arginine at position 144 of the protein [5]. This structural alteration significantly impacts how interleukin 13 binds to its receptor, altering its signaling efficiency and biological activity [5] [2]. The reference A allele (encoding glutamine) produces a highly active form of the cytokine that promotes Th2-type allergic inflammation [2] [3]. Conversely, the variant G allele (encoding arginine) reduces Th2 pathway activity but shifts the immune balance toward Th17-mediated inflammatory pathways [3] [6].
Key Insight: This variant acts as an evolutionary immune pivot, where the allele that protects you from asthma and eczema simultaneously increases your susceptibility to psoriasis.
Location: IL13. Chromosome 5 · 5q31.1 · 132.7 Mb
Estimated prevalence by population
Global 5.7%; European 4.1%; African 3.3%; East Asian 10.8%; South Asian 8.4%; Americas 10.9%; Ashkenazi 5.4%; Finnish 15.1%; Middle Eastern 3.6%; Amish 1.6%.
Estimated AA genotype frequency.
Global 34.6%; European 32.2%; African 29.9%; East Asian 44.1%; South Asian 41.2%; Americas 44.2%; Ashkenazi 35.7%; Finnish 47.5%; Middle Eastern 30.8%; Amish 22.1%.
Estimated AG genotype frequency.
Global 59.7%; European 63.7%; African 66.8%; East Asian 45.1%; South Asian 50.4%; Americas 44.9%; Ashkenazi 58.9%; Finnish 37.4%; Middle Eastern 65.5%; Amish 76.3%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Organ Systems
Respiratory Health
Asthma. Evidence: 10/10. Source: PMID 29273806. ~1.2x Higher Risk.
Skin & Hair Conditions
Atopic Eczema. Evidence: 10/10. Source: PMID 34116867. ~1.18x Higher Risk.
Psoriasis. Evidence: 8/10. Source: PMID 19169254. Typical Risk.
Immunity & Inflammation
Allergy & Hypersensitivity
Allergic Rhinitis. Evidence: 10/10. Source: PMID 31361310. ~1.12x Higher Risk.
Showing effects for A/G genotype
Asthma. Evidence: 10/10. Source: PMID 29273806. Slightly Higher Risk.
Atopic Eczema. Evidence: 10/10. Source: PMID 34116867. Slightly Higher Risk.
Psoriasis. Evidence: 8/10. Source: PMID 19169254. Slightly Higher Risk.
Allergic Rhinitis. Evidence: 10/10. Source: PMID 31361310. Slightly Higher Risk.
Showing effects for G/G genotype
Asthma. Evidence: 10/10. Source: PMID 29273806. Typical Risk.
Atopic Eczema. Evidence: 10/10. Source: PMID 34116867. Typical Risk.
Psoriasis. Evidence: 8/10. Source: PMID 19169254. ~1.27x Higher Risk.
Allergic Rhinitis. Evidence: 10/10. Source: PMID 31361310. Typical Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Carrying two copies of the A allele results in a highly active form of the interleukin 13 cytokine [1]. This hyper-reactivity drives the immune system toward a T-helper type 2 (Th2) response, which is responsible for allergic reactions [1] [2]. Large-scale genetic studies consistently link this genotype to elevated levels of circulating IgE antibodies, the primary triggers of allergic symptoms [2] [3]. Consequently, individuals with this genotype face a significantly higher risk of developing childhood and persistent asthma [3] [4]. Skin barrier vulnerability is also increased, leading to a higher prevalence of atopic eczema and allergic rhinitis [4] [5]. Interestingly, this strong Th2 bias provides a natural shield against Th17-mediated autoimmune conditions, resulting in a lower risk of psoriasis [6].
Increased susceptibility to asthma and breathing difficulties; Higher likelihood of developing atopic eczema and hay fever; Lower risk of developing autoimmune psoriasis.
Sample genotype: AG (Heterozygous)
Having one copy of the A allele and one copy of the G allele places the immune system at a biological crossroads [1]. The presence of the A allele maintains a moderate tendency toward Th2-mediated allergic inflammation, elevating IgE antibody levels [1] [2]. This translates to a slightly increased risk of developing asthma, eczema, and allergic rhinitis compared to those with the G/G genotype [2] [3]. At the same time, the presence of the G allele introduces a mild susceptibility to Th17-mediated autoimmune pathways [4]. Because of this dual genetic influence, individuals with this genotype do not experience the extreme risks of either side but remain moderately susceptible to both atopic and psoriatic conditions [4] [5].
Mildly elevated risk of asthma and seasonal allergies; Slightly increased susceptibility to dry, itchy eczema; Slightly higher risk of psoriasis compared to A/A homozygotes.
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele results in a less active Th2 immune pathway, which significantly lowers the risk of allergic diseases [1]. This genotype is strongly associated with lower levels of IgE antibodies, providing natural protection against asthma, atopic eczema, and hay fever [1] [2]. However, dampening the Th2 pathway allows the Th17 autoimmune pathway to become more active [3]. As a result, individuals with this genotype have a significantly higher susceptibility to psoriasis and psoriatic arthritis [3] [4]. Clinical studies also suggest that asthmatic individuals with this genotype may respond better to standard inhaled corticosteroid therapies [5]. This genotype represents a classic evolutionary trade-off between allergy protection and autoimmune risk [3].
Significantly lower risk of developing asthma and eczema; Increased susceptibility to psoriasis and psoriatic skin plaques; Potentially better response to certain asthma controller medications.
Variants with shared genetic architecture
rs848 · IL13 Gene · Chr 5 · Asthma and Eczema
rs1295686 · IL13 Gene · Chr 5 · Asthma and Eczema Risk
rs1295685 · IL13 Gene · Chr 5 · Allergy and Skin Health
Genetic variants of IL-13 signalling and human asthma and atopy.
A genome-wide association study of plasma total IgE concentrations in the Framingham Heart Study.
Eight novel susceptibility loci and putative causal variants in atopic dermatitis.
Genome-wide scan reveals association of psoriasis with IL-23 and NF-kappaB pathways.
Apremilast Pharmacogenomics in Russian Patients with Moderate-to-Severe and Severe Psoriasis.
Content updated August 2026.
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