Men's fertility-friendly underwear may be briefs without benefits

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Jun 17 2026

A new review finds that looser underwear may help keep testes cooler and support some sperm measures, but the evidence stops short of proving it can boost a man’s chances of fatherhood.

Study: Garment fit, scrotal thermoregulation, and male fertility outcomes: a narrative review. Image Credit: Friva / Shutterstock

In a recent narrative review published in the journal Translational Andrology and Urology, researchers synthesized evidence on whether underwear fit and fabric characteristics are associated with scrotal temperature, semen quality, reproductive hormones, and male fertility outcomes.

Background

Could something as simple as the underwear men wear influence their chances of fatherhood?

Male infertility affects many couples worldwide. With growing interest in lifestyle factors and their possible effects on men's reproductive health, scrotal temperature has become one area of concern. The testes need to remain several degrees below core body temperature to produce a normal quantity and quality of sperm.

Tight-fitting underwear could decrease ventilation and therefore cause increased temperature retention around the testes, thus contributing to poorer semen quality. Conversely, loose-fitting underwear could improve testicular cooling.

Underwear labeled “fertility friendly” appears popular among consumers, but scientific findings remain inconsistent. Therefore, more research is needed to determine whether clothing affects fertility outcomes in the real world.

About the Study

The investigators conducted a structured narrative review of published research examining the relationship between underwear choice, scrotal temperature, and male reproductive health.

The authors conducted a structured literature search in PubMed, the sole database used, for studies published up to April 20, 2025. The investigators used search terms that included types of underwear, scrotal or testicular temperature, sperm quality, semen quality, and fertility outcomes.

Only peer-reviewed studies involving human participants and published in English were considered eligible. Observational studies, including cross-sectional, case-control, and cohort studies, as well as intervention studies, that assessed underwear fit or type of garment, fabric composition, or heat exposure related to reproductive outcomes were included. Experimental investigations of controlled increases in testicular temperature were also reviewed to provide a biological context for the effects of heat on spermatogenesis.

Researchers examined studies reporting outcomes such as semen volume, sperm concentration, total sperm count, sperm motility, sperm morphology, sperm DNA integrity, reproductive hormone levels, and fertility-related measures.

Titles and abstracts were screened before full-text assessment of relevant articles. Information regarding study populations, sample sizes, exposure characteristics, and reproductive outcomes was extracted and compared. Researchers compared results qualitatively rather than through statistical pooling or meta-analysis because the study designs varied.

Study Results

The reviewed evidence demonstrated that the choice of underwear may influence the testicular environment, although findings across studies were not entirely consistent. Several physiological studies have shown that wearing tight-fitting underwear increases testicular temperature compared with either loose-fitting underwear or no undergarments.

In controlled physiologic testing, tight-fitting undergarments increased scrotal temperature by approximately 1°C, while induced-heating models showed that sustained 1–2°C increases in testicular temperature could negatively affect spermatogenesis.

Evidence comparing boxer shorts and briefs remains inconsistent. Several early studies found no meaningful differences in sperm concentration, motility, or morphology among men wearing loose or tight underwear. However, other studies suggest that wearing tight clothing increases the risk of being dyspermic, meaning having abnormal semen quality, and this is particularly true for men who wear tight-fitting underwear in combination with tight trousers.

More recent research has provided additional support for the potential benefits of looser underwear. Some observational studies reported associations between looser underwear and better semen measures, including lower odds of low motile sperm concentration, fewer sperm neck abnormalities, and lower sperm DNA damage, although findings varied by study.

A cross-sectional study involving more than 650 men attending a fertility center found that boxer-short users had approximately 25% higher sperm concentration and 17% higher total sperm count than men who wore tighter underwear. The same study also reported 14% lower follicle-stimulating hormone (FSH) among boxer-short users, but found no associations with other reproductive outcomes.

Despite these findings, the evidence linking underwear type to actual fertility outcomes remained limited. A prospective study involving couples attempting conception found minor differences in semen characteristics among various underwear categories, but no significant differences in conception delay, infertility rates, or time to pregnancy. This shows that although the type of underwear worn may affect how well a man’s reproductive system functions in a laboratory setting, such differences have not yet been shown to translate into improved real-world fertility outcomes.

The review also examined the role of fabric composition, and there is little information available regarding the comparison of natural versus synthetic fabrics under normal conditions.

Textile studies suggest cotton-containing fabrics may release heat more effectively than polyester-based fabrics, but these findings are indirect and are influenced by fabric structure and layering. No real-world human fertility studies directly comparing natural versus synthetic underwear fabrics are available. 

One small experimental study reported reversible azoospermia among men wearing polyester devices continuously for prolonged periods; however, the unusual exposure conditions and limited sample size reduced the applicability of these findings. The review also notes that the proposed mechanism was electrostatic rather than thermal, biologically unconventional, and not independently validated.

Experimental heat-exposure studies support the biological sensitivity of spermatogenesis to sustained testicular warming, although not all models of modest scrotal temperature increase produced measurable semen impairment.

Increased testicular temperature can negatively affect sperm production, reduce sperm counts, and increase the DNA fragmentation index. Importantly, many of these effects appeared reversible after heat exposure ended. This information suggests that temperature regulation may influence male reproductive health, but it is unlikely that wearing underwear alone will significantly affect male fertility.

Conclusions

The review concluded that the choice of underwear may modestly influence male reproductive physiology by altering scrotal temperature. Some studies indicate men with loose-fitting underwear have slightly higher sperm production measures than men with tight-fitting underwear; however, there is currently no consistent evidence that improved semen parameters due to these types of garments lead to better fertility outcomes. Evidence regarding fabric composition is particularly limited.

Overall, underwear selection should be considered a supportive lifestyle factor rather than a proven fertility intervention, while broader health behaviors remain more influential determinants of reproductive success.

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