Genetic Study Shows No Direct Link Between Smoking and Urticaria Risk
Does smoking cause hives? A new genetic study and what it means for you
If you get hives (medically called urticaria), you may have heard different things about smoking. Some studies say smoking raises the risk, others say it might protect against allergic reactions. A recent genetic study tried a different approach to see if smoking actually causes hives. The short version: the study found no clear genetic evidence that smoking causes urticaria.
A plain-language summary
Researchers used a method that looks at genes to test whether smoking is likely to cause hives. They checked three kinds of smoking exposure: currently smoking, past smoking, and living with smokers (secondhand smoke). Across large genetic datasets, they did not find convincing proof that any of these actually cause urticaria. One result for household smoking looked borderline, but other checks showed it was probably not a real causal link.
How the study worked — in everyday language
The study used a technique called Mendelian randomization. This uses genetic differences that people are born with as a natural experiment. Because genes are fixed at birth, this method helps separate true cause-and-effect from other tangled factors like lifestyle or social differences.
The researchers looked at three smoking “phenotypes,” meaning three types of exposure:
- Current tobacco smoking.
- Past tobacco smoking.
- Smoking or smokers in the household (a measure of secondhand smoke).
All participants were of European ancestry. The genetic datasets were large: about 462,000 people for current smoking, 425,000 for past smoking, 425,000 for household smoking, and nearly 497,000 people in the urticaria dataset.
To be careful, the team selected genetic markers using strict rules so they were likely to reflect smoking behavior and not something else. They ran a main analysis and then several different checks to make sure the results were robust. These checks tested whether any single gene was driving the results, whether different genes gave conflicting signals, and whether the direction of cause and effect might be reversed.
What they found
Here are the key results, reported as odds ratios (OR). An OR above 1 suggests higher risk, below 1 suggests lower risk. If the confidence range crosses 1 and the P value is not small, the result is not statistically convincing.
Past tobacco smoking: No significant link with urticaria (OR 1.13; 95% CI 0.97–1.31; P = .124). That means the evidence did not show a clear causal effect.
Current tobacco smoking: No significant link with urticaria (OR 0.62; 95% CI 0.33–1.14; P = .124). Again, the result did not reach statistical significance.
Smoking or smokers in the household (secondhand smoke): The main analysis showed a borderline association (OR 4.38; 95% CI 1.00–19.20; P = .050). But other analytic approaches did not reproduce that finding, and the researchers judged it insufficient to claim a causal relationship. This secondhand smoke measure had fewer strong genetic markers available and may be more affected by household and socioeconomic factors.
Across the analyses, tests for inconsistent results, genes affecting multiple traits, or single genes skewing the outcome did not show major problems. A test for reverse causality also did not suggest that having urticaria changes smoking-related genetics rather than the other way around.
What this does and doesn’t mean
This study suggests that there is no clear genetic proof that smoking causes hives. That challenges earlier observational studies that gave mixed messages. Observational studies can be distorted by other factors — for example, people who smoke might differ from non-smokers in many ways that affect health.
However, the results do not rule out several possibilities:
- Smoking might sometimes act as an immediate trigger or make hives worse in some people.
- The intensity and duration of smoking could matter and weren’t captured in detail here.
- Different types of urticaria (for example, chronic vs. short-lived hives) might react differently to tobacco exposure.
- The study included only people of European ancestry, so findings may not apply to everyone.
Strengths and limitations to keep in mind
Strengths: The study used large genetic datasets and several methods to check the findings, which reduces the chance that the result is a fluke.
Limitations: The research did not look at specific urticaria subtypes, it only included European populations, and the secondhand smoke measure had fewer reliable genetic markers. Because of those limits, the authors call for larger, more detailed studies across different populations and types of urticaria.
Practical takeaways
For people worried about hives, this study says there’s no strong genetic evidence that smoking is a direct cause. Still, smoking has many well-established harms, so quitting remains an important step for overall health. If you notice smoking seems to trigger or worsen your hives, bring that up with your clinician.
If you have new, changing, or severe skin symptoms — especially if they are painful, bleeding, infected, spreading fast, or making it hard to breathe or swallow — seek medical help right away.
If you track skin changes over time, keeping a simple photo diary can help you notice patterns and be ready to discuss them with your doctor.
Disclaimer
This article explains the findings of a research study in plain language. It is not medical advice. If you have questions about urticaria or smoking and your health, talk with your doctor or a dermatologist.
Sources
- No Evidence for a Genetic Causal Association Between Smoking and Urticaria: A Mendelian Randomization Study. Clin Cosmet Investig Dermatol. Published 2026 Aug 21. doi:10.2147/CCID.S624506 (Source: Clin Cosmet Investig Dermatol, 2026)
- Hjern A, Hedberg A, Haglund B, Rosén M. Does tobacco smoke prevent atopic disorders? A study of two generations of Swedish residents. doi:10.1046/j.1365-2222.2001.01096.x (Source: study cited in the original article)