What you carry at this position in your DNA and what research says about it.
Asthma and Eczema: 10/10 evidence, 22 publications.
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Sample genotype (not yours): A/A
Higher Asthma and Eczema Risk but Lower Arthritis Risk
Allergic conditions like asthma and eczema are more common with this profile, though it provides protection against psoriatic arthritis.
What this genotype means: Increased risk of asthma and eczema; Reduced risk of psoriatic arthritis; Poorer response to ustekinumab.
Sample genotype (not yours): A/C
Moderately Higher Asthma and Eczema Risk
A moderate increase in the risk of asthma and allergic skin conditions is associated with this profile. It may also influence response to certain psoriasis medications.
What this genotype means: Moderately increased risk of asthma and eczema; Slightly poorer response to ustekinumab.
Sample genotype (not yours): C/C
Typical Asthma Risk but Higher Psoriatic Arthritis Risk
Typical baseline risks for asthma and eczema are expected with this profile. However, there is an increased susceptibility to developing psoriatic arthritis.
What this genotype means: Typical baseline risk of asthma and eczema; Increased risk of psoriatic arthritis; Typical response to ustekinumab.
Gene function and biological role
Gene Function: Interleukin 13 is an immunoregulatory cytokine produced primarily by activated T helper type 2 cells. It plays a critical role in driving allergic inflammation, stimulating immunoglobulin E production, and promoting airway hyperreactivity [1] [2]. Excessive production of this cytokine is a hallmark of atopic conditions, including asthma and eczema [3]. Conversely, downregulating these pathways can sometimes alter susceptibility to other autoimmune conditions [4].
Variant Impact: Located in the 3 prime untranslated region of the IL13 gene, this single nucleotide polymorphism can influence how the genetic blueprint is regulated and translated into protein. The sequence change alters the stability of the messenger RNA, which directly impacts the amount of interleukin 13 cytokine produced by immune cells [5]. Higher levels of the cytokine promote allergic responses, while lower levels shift the immune balance [2]. This molecular shift explains the opposing risks observed for allergic and autoimmune diseases [4].
Key Insight: The same genetic variant that increases the risk for asthma and eczema actually helps protect against developing psoriatic arthritis.
Location: IL13. Chromosome 5 · 5q31.1 · 132.7 Mb
Estimated prevalence by population
Global 12.0%; European 4.2%; African 24.7%; East Asian 10.6%; South Asian 8.4%; Americas 13.5%; Ashkenazi 6.3%; Finnish 15.2%; Middle Eastern 6.0%; Amish 1.6%.
Estimated AA genotype frequency.
Global 40.6%; European 32.5%; African 50.0%; East Asian 43.9%; South Asian 41.2%; Americas 46.5%; Ashkenazi 37.7%; Finnish 47.6%; Middle Eastern 37.0%; Amish 22.0%.
Estimated AC genotype frequency.
Global 47.5%; European 63.3%; African 25.3%; East Asian 45.5%; South Asian 50.4%; Americas 39.9%; Ashkenazi 56.0%; Finnish 37.3%; Middle Eastern 57.0%; Amish 76.4%.
Estimated CC genotype frequency.
Showing effects for A/A genotype
Organ Systems
Respiratory Health
Asthma. Evidence: 10/10. Source: PMID 31361310. Increased Risk.
Skin & Hair Conditions
Atopic Eczema. Evidence: 8/10. Source: PMID 23727859. ~1.4x Risk.
Immunity & Inflammation
Autoimmune Diseases
Psoriatic Arthritis. Evidence: 6/10. Source: PMID 35507331. Lower Risk.
Pharmacogenomics
Immunosuppressant & Biologic Response
Ustekinumab Response. Evidence: 5/10. Source: PMID 27977334. Poorer Response.
Showing effects for A/C genotype
Asthma. Evidence: 10/10. Source: PMID 31361310. Slightly Increased.
Atopic Eczema. Evidence: 8/10. Source: PMID 23727859. Slightly Increased.
Psoriatic Arthritis. Evidence: 6/10. Source: PMID 35507331. Typical Risk.
Showing effects for C/C genotype
Asthma. Evidence: 10/10. Source: PMID 31361310. Typical Risk.
Atopic Eczema. Evidence: 8/10. Source: PMID 23727859. Typical Risk.
Psoriatic Arthritis. Evidence: 6/10. Source: PMID 35507331. ~1.28x Risk.
Ustekinumab Response. Evidence: 5/10. Source: PMID 27977334. Typical Response.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Allergic responses are heightened under this genetic profile due to increased interleukin 13 activity. Large-scale genetic studies show a clear link to a higher risk of developing asthma [1] and atopic eczema [2]. Interestingly, the same immune profile that drives allergy appears to protect the joints. Research indicates a significantly lower risk of developing psoriatic arthritis compared to other genotypes [3]. If psoriasis is present, there is also a higher likelihood of a poorer response to the biologic therapy ustekinumab [4]. Maintaining a healthy skin barrier and avoiding environmental triggers like tobacco smoke can help manage these risks [5].
Increased risk of asthma and eczema; Reduced risk of psoriatic arthritis; Poorer response to ustekinumab.
Sample genotype: AC (Heterozygous)
Immune system regulation is slightly altered with this intermediate genetic profile. Clinical data show a moderately elevated risk of developing asthma [1] and allergic diseases like eczema [2]. The presence of a single A allele is also associated with a potentially poorer response to the psoriasis drug ustekinumab [3]. Unlike the double-A profile, this genotype does not appear to offer strong protection against psoriatic arthritis [4]. Managing environmental exposures, particularly avoiding secondhand smoke, is highly beneficial for respiratory health [5].
Moderately increased risk of asthma and eczema; Slightly poorer response to ustekinumab.
Sample genotype: CC (Homozygous)
Baseline immune function remains typical for allergic pathways under this genetic profile. Studies show no elevated risk for asthma [1], eczema [2], or general allergic diseases [3]. However, the major C allele is a recognized risk factor for joint inflammation in individuals with psoriasis. Research indicates a significantly higher risk of developing psoriatic arthritis [4] [5]. On the positive side, individuals with this genotype tend to show a typical, favorable response to biologic treatments like ustekinumab if needed [6].
Typical baseline risk of asthma and eczema; Increased risk of psoriatic arthritis; Typical response to ustekinumab.
Variants with shared genetic architecture
rs20541 · IL13 Gene · Chr 5 · Asthma and Eczema Risk
rs1295686 · IL13 Gene · Chr 5 · Asthma and Eczema Risk
rs1295685 · IL13 Gene · Chr 5 · Allergy and Skin Health
Shared genetic origin of asthma, hay fever and eczema elucidates allergic disease biology.
Association between IL13 polymorphisms and psoriatic arthritis is modified by smoking.
High-density genotyping study identifies four new susceptibility loci for atopic dermatitis.
Pharmacogenetics of ustekinumab in patients with moderate-to-severe plaque psoriasis.
Content updated August 2026.
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