What you carry at this position in your DNA and what research says about it.
Asthma and Eczema Risk: 8/10 evidence, 43 publications.
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Sample genotype (not yours): T/T
Higher Risk of Asthma and Eczema
Two copies of the T allele are associated with an increased susceptibility to allergic conditions like asthma and eczema. This profile may also lead to a weaker immune response to the hepatitis B vaccine.
What this genotype means: Higher risk of developing atopic eczema; Increased susceptibility to asthma and allergies; Potentially lower antibody response to hepatitis B vaccine.
Sample genotype (not yours): C/C
Typical Risk of Asthma and Eczema
Two copies of the C allele are associated with a typical, lower risk of asthma and eczema. However, this profile is linked to a slightly increased susceptibility to psoriasis.
What this genotype means: Lower risk of developing asthma and eczema; Typical, effective response to hepatitis B vaccination; Slightly increased risk of psoriasis.
Sample genotype (not yours): T/C
Slightly Higher Risk of Asthma and Eczema
A single copy of the T allele is linked to a moderately increased risk of eczema, asthma, and allergic responses. It is also associated with a potentially reduced response to the hepatitis B vaccine.
What this genotype means: Moderately increased risk of eczema and skin allergies; Slightly elevated risk of asthma; Slightly lower response rate to hepatitis B vaccination.
Gene function and biological role
Gene Function: The IL13 gene encodes interleukin 13, a critical cytokine secreted primarily by T-helper type 2 cells [1]. This protein plays a central role in regulating the body's immune response, particularly in driving allergic inflammation [1]. It stimulates B-cells to produce immunoglobulin E antibodies and promotes the recruitment of inflammatory cells to tissues [2]. Overexpression of interleukin 13 is a well-established driver of airway hyperresponsiveness and skin barrier disruption [2]. Consequently, genetic variations in this gene are heavily studied in connection with allergic and inflammatory diseases [3].
Variant Impact: The rs1295686 variant is an intronic change located within the IL13 gene on chromosome 5. This genetic variation is in tight linkage disequilibrium with functional variants that alter interleukin 13 expression levels. The minor T allele is consistently associated with increased levels of total serum immunoglobulin E [4]. It also correlates with heightened inflammatory responses in the airways and skin [3]. Conversely, the major C allele is linked to a typical immune profile but may slightly increase susceptibility to psoriasis [5].
Key Insight: The same genetic variant that increases your risk for allergic conditions like asthma and eczema actually provides protection against psoriasis.
Location: IL13. Chromosome 5 · 5q31.1 · 132.7 Mb
Estimated prevalence by population
Global 17.2%; European 4.3%; African 42.6%; East Asian 10.7%; South Asian 9.5%; Americas 15.6%; Ashkenazi 7.2%; Finnish 15.1%; Middle Eastern 8.2%; Amish 1.6%.
Estimated TT genotype frequency.
Global 39.6%; European 32.7%; African 45.3%; East Asian 44.0%; South Asian 42.6%; Americas 47.8%; Ashkenazi 39.3%; Finnish 47.5%; Middle Eastern 40.8%; Amish 22.1%.
Estimated TC genotype frequency.
Global 43.2%; European 63.0%; African 12.0%; East Asian 45.2%; South Asian 47.9%; Americas 36.7%; Ashkenazi 53.5%; Finnish 37.3%; Middle Eastern 51.0%; Amish 76.3%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Organ Systems
Skin & Hair Conditions
Atopic Eczema. Evidence: 10/10. Source: PMID 23042114. Increased Risk.
Psoriasis. Evidence: 7/10. Source: PMID 25574825. Lower Risk.
Respiratory Health
Asthma. Evidence: 8/10. Source: PMID 20860503. ~1.3x Increased Risk.
Childhood Asthma. Evidence: 8/10. Source: PMID 24241537. ~1.6x Increased Risk.
Immunity & Inflammation
Infection Susceptibility & Resistance
Hepatitis B Vaccine Response. Evidence: 5/10. Source: PMID 21111021. Poorer Response.
Showing effects for C/C genotype
Atopic Eczema. Evidence: 10/10. Source: PMID 23042114. Typical Risk.
Psoriasis. Evidence: 7/10. Source: PMID 25574825. Increased Risk.
Asthma. Evidence: 8/10. Source: PMID 20860503. Typical Risk.
Childhood Asthma. Evidence: 8/10. Source: PMID 24241537. Typical Risk.
Hepatitis B Vaccine Response. Evidence: 5/10. Source: PMID 21111021. Typical Response.
Showing effects for T/C genotype
Atopic Eczema. Evidence: 10/10. Source: PMID 23042114. Slightly Increased.
Psoriasis. Evidence: 7/10. Source: PMID 25574825. Typical Risk.
Asthma. Evidence: 8/10. Source: PMID 20860503. ~1.15x Increased Risk.
Childhood Asthma. Evidence: 8/10. Source: PMID 24241537. ~1.3x Increased Risk.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Two copies of the T allele significantly influence how the immune system reacts to environmental triggers. Baseline levels of immunoglobulin E, the antibody responsible for allergic reactions, tend to be higher with this genetic profile [1]. This elevated antibody production increases the likelihood of developing atopic eczema and skin barrier issues [2]. Airway tissues also show heightened sensitivity, which raises the probability of developing asthma [3]. Clinical studies have identified a particularly strong link to childhood-onset asthma in those with this genotype [3]. Furthermore, research indicates that this genetic makeup may result in a less robust antibody response following hepatitis B vaccination [4]. However, this active inflammatory profile appears to offer a protective effect against other conditions. Specifically, it is associated with a lower susceptibility to developing psoriasis [5].
Higher risk of developing atopic eczema; Increased susceptibility to asthma and allergies; Potentially lower antibody response to hepatitis B vaccine; Reduced risk of developing psoriasis.
Sample genotype: CC (Homozygous)
Two copies of the common C allele generally protect against the overactive allergic responses driven by interleukin 13. Baseline levels of immunoglobulin E antibodies typically remain lower in individuals with this genetic profile [1]. Consequently, there is a significantly lower risk of developing atopic eczema and allergic skin conditions [2]. Susceptibility to both childhood-onset and adult asthma is also maintained at a standard, baseline level [3]. Immunization efforts are highly effective, as this genotype is linked to a strong, typical immune response to the hepatitis B vaccine [4]. The primary trade-off of this balanced immune state is a slightly elevated risk of developing psoriasis [5]. This autoimmune skin condition is driven by a different inflammatory pathway that is more active in this genotype [5]. Ultimately, this profile represents a highly favorable genetic makeup for avoiding common allergies [2].
Lower risk of developing asthma and eczema; Typical, effective response to hepatitis B vaccination; Slightly increased risk of psoriasis.
Sample genotype: TC (Heterozygous)
A single copy of the T allele places the immune system's reactivity between the two homozygous profiles. Total serum immunoglobulin E levels are moderately elevated, which can trigger allergic symptoms [1]. Clinical studies have demonstrated a heightened risk of developing atopic dermatitis and skin barrier issues [2]. Airway sensitivity is also slightly elevated, leading to an increased probability of asthma onset [3]. Furthermore, research indicates that carriers of a single T allele may experience a less effective immune response to hepatitis B immunization [4]. This intermediate profile means that while risks are elevated, they are not as pronounced as in those with two copies of the T allele [3]. On the other hand, this genetic makeup maintains a typical risk profile for psoriasis, balancing the opposing inflammatory pathways [5]. Overall, this genotype represents a moderate genetic predisposition to allergic sensitivity [2].
Moderately increased risk of eczema and skin allergies; Slightly elevated risk of asthma; Slightly lower response rate to hepatitis B vaccination.
Variants with shared genetic architecture
rs20541 · IL13 Gene · Chr 5 · Asthma and Eczema Risk
rs848 · IL13 Gene · Chr 5 · Asthma and Eczema
rs1295685 · IL13 Gene · Chr 5 · Allergy and Skin Health
Interleukin-13 +1923C/T polymorphism is associated with asthma risk: a meta-analysis.
A genome-wide association study of plasma total IgE concentrations in the Framingham Heart Study.
A large-scale, consortium-based genomewide association study of asthma.
Content updated August 2026.
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