What Does Icing Your Balls Do for Your Health?

Cooling your testicles lowers scrotal temperature closer to the range where sperm production works best, and there is real clinical evidence that sustained scrotal cooling can modestly improve sperm count and motility in men with fertility problems. The practice has a more complicated relationship with testosterone, and the casual wellness claims you see online tend to outrun the science. What the research actually shows is more specific and more interesting than most of the internet advice suggests.

Why Testicle Temperature Matters

Your testicles hang outside your body for a reason. The temperature inside the scrotum runs about 2 to 3 degrees Celsius below core body temperature, and that gap is not accidental. The scrotal skin is thin, has almost no subcutaneous fat, and carries more sweat glands than surrounding skin, all of which help shed heat efficiently.¹ Sperm production operates best in a narrow thermal window of roughly 34 to 35 degrees Celsius. When researchers compared spermatogenic cell development at 35°C versus normal body temperature of 37°C in lab cultures, the cells grown at the cooler temperature produced significantly more developed sperm cells at every stage, while the warmer cultures showed higher rates of cell death.²

The body has built-in hardware to regulate this. The cremaster muscle pulls the testicles closer to the body in cold conditions and lets them drop lower in warm ones. The pampiniform plexus, a network of veins wrapping around the testicular artery, works like a heat exchanger, cooling arterial blood before it reaches the testes. When people talk about “icing your balls,” they are essentially trying to assist or amplify a system the body already runs on its own.

What Heat Does to Sperm

The evidence that elevated scrotal temperature harms sperm quality is strong. A meta-analysis pooling data from multiple studies found that high ambient temperature was associated with significant drops in semen volume, sperm concentration, total sperm count, motility, and normal sperm shape.³ The declines were not subtle. Normal morphology took the biggest hit, followed by motility and concentration.

Experimental studies in men confirm this pattern. When researchers deliberately raised scrotal temperature in healthy volunteers, sperm concentration and motility dropped significantly, and markers of oxidative stress in seminal fluid went up. The damage was reversible once the heat exposure stopped.⁴ A separate study looking at mild but sustained scrotal warming found that sperm DNA integrity was impaired within about 20 days, with motility and viability declining shortly after. All the measured parameters returned to baseline roughly 73 days after the heat exposure ended.⁵

That roughly 10-week recovery timeline matters. Spermatogenesis takes about 74 days from start to finish, so sperm being ejaculated today reflect the conditions your testes experienced two to three months ago. Damage from a hot tub binge in July would show up in a semen analysis in September and clear up by November. This is why fertility specialists ask about heat exposure history when evaluating male factor infertility.

Can Cooling Actually Improve Fertility?

If heat hurts sperm, the logical follow-up is whether deliberate cooling helps. The answer, at least for men who already have suboptimal sperm parameters, is a cautious yes. In a study of men with poor semen quality, nocturnal scrotal cooling using a directed air stream lowered scrotal temperature by about 1°C and produced a highly significant increase in sperm concentration and total sperm output after 12 weeks. Motility and morphology also improved, though less dramatically.⁶ The same study noted that the highest scrotal temperatures in these patients occurred during rest and sleep, not during physical activity, which is why nighttime cooling specifically was targeted.

Another trial focused on men with a history of undescended testes (a known risk factor for impaired fertility) found that nocturnal cooling significantly increased sperm concentration and total count after 8 and 12 weeks. The changes in motility and morphology were less clear-cut.⁷ A study evaluating wearable scrotal cooling devices reported increases in sperm motility (from about 25% to 29%) and vitality (from about 65% to 72%) after use.⁶

These numbers are real but modest. For a man with borderline fertility, bumping sperm motility from 25% to 29% could matter, especially when combined with other interventions. For a man with normal semen parameters, there is no evidence that scrotal cooling pushes an already-healthy count higher in any meaningful way. The research has focused almost entirely on men with diagnosed fertility problems, not on optimization of already-normal function.

The Testosterone Angle

This is where online wellness advice tends to get ahead of the science. You will find claims that icing your testicles “boosts testosterone,” and there is a kernel of truth buried in the animal research, but no direct human evidence to support the claim as stated.

What we know is that heat suppresses testosterone production. In mouse studies, repeated testicular heating caused stress-related damage to Leydig cells (the cells that produce testosterone), leading to decreased testosterone output.⁸ At the enzyme level, a key step in testosterone synthesis involves an enzyme called CYP17, which turns out to be remarkably sensitive to temperature. When researchers raised testicular temperature from 31°C to 38°C for just three hours, CYP17 activity dropped by 57% in whole testes and 39% in isolated Leydig cells.⁹ Research in zebrafish has shown that a temperature-sensitive channel called Trpv4, which activates above certain temperature thresholds, can trigger Leydig cell death at elevated temperatures.¹⁰

So heat can clearly impair testosterone production in animal models and in laboratory cell studies. The leap people make is: “If heat lowers testosterone, cold must raise it.” That logic is not entirely wrong in principle, but it skips several important steps. No published human trial has shown that applying cold to the scrotum raises serum testosterone levels. The scrotal cooling studies that exist measured sperm parameters, not testosterone. It is plausible that avoiding chronic scrotal overheating helps maintain normal testosterone production, but that is very different from the claim that ice packs will boost your T levels above baseline. Think of it less as a performance enhancer and more as avoiding an interference pattern: keeping things at the right temperature so normal function isn’t disrupted.

Exercise and Scrotal Warming

If you exercise regularly, you might wonder whether your workouts are cooking your sperm. The answer is nuanced. A study measuring scrotal temperature during naked running (the researchers were thorough) found a distinctive pattern: while skin temperature elsewhere on the body dropped at the start of exercise, scrotal temperature actually rose. After the run ended, the pattern reversed, and scrotal temperature fell while other skin temperatures climbed.¹¹ This makes sense. During exercise, blood flow redistributes toward working muscles, and the increased metabolic heat in the groin area temporarily overwhelms the scrotum’s cooling systems.

Does this transient warming actually damage sperm? Probably not for normal exercise durations. A study in stallions exercised strenuously for 90 minutes under hot, humid conditions found that scrotal temperature rose by about 1.5°C compared to resting animals, but no differences in sperm quality were detected between the exercised and control groups.¹² The researchers concluded that the kind of transient temperature spike that comes with a hard workout is unlikely to harm spermatogenesis on its own. In rams, scrotal temperature regulation was effective enough that scrotal temperature stayed stable during exercise even as core body temperature climbed.¹³

The takeaway for physically active people: your body’s built-in cooling systems handle normal exercise-related heat well. If you are genuinely concerned about fertility, the evidence suggests that prolonged sedentary heat exposure (hours of sitting, tight clothing, laptop on your lap) is a bigger threat than your training sessions.

Why the Compliance Problem Matters

Even where scrotal cooling has shown benefits for fertility, there is a practical barrier that the research openly acknowledges: people do not stick with it. In the study of wearable scrotal cooling devices, about 77% of users wore the devices less than the recommended duration. Participants reported that the devices were uncomfortable (about a third of users), interfered with daily activities (about a fifth), and lost their cooling effect too quickly (about one in seven).⁶

This is worth keeping in mind if you are considering any form of regular testicular cooling. The studies showing fertility benefits used sustained, controlled cooling over weeks to months. Briefly holding an ice pack against your scrotum for a few minutes is a very different stimulus from wearing a cooling device nightly for 12 weeks. The sperm production cycle takes roughly 74 days, so meaningful changes to sperm quality require consistent temperature management over that entire window. A one-off cold application is unlikely to produce measurable effects on semen parameters.

Risks of Overdoing It

Cold exposure carries its own hazards when taken too far. Direct ice-on-skin contact can cause frostbite or cold burns, and the scrotal skin is thinner and more sensitive than most other body areas. The dartos muscle in the scrotum contracts vigorously in response to cold, pulling the testes tight against the body. At very low temperatures (around 15°C), this contractile response actually becomes less effective than at normal scrotal temperature, meaning the tissue’s own protective reflexes can be impaired by extreme cold.

There is also no evidence that colder is better. The research showing sperm production improvements used mild cooling, typically lowering scrotal temperature by about 1°C. The goal is to bring scrotal temperature down to the 34 to 35°C range where spermatogenesis works best, not to make the tissue as cold as possible. Going well below that range does not help and could cause tissue damage. If you are going to experiment with scrotal cooling, a cloth-wrapped cold pack or a brief cool shower is a world apart from sitting on a bag of ice.

When Temperature Is Not the Real Problem

One common misconception is that any fertility issue related to testicular position must be a temperature problem. Undescended testes (cryptorchidism) are the classic example. It has long been assumed that the elevated temperature inside the body damages the undescended testes, causing both infertility and increased cancer risk. But more recent research challenges this view. A study examining gonocyte development in boys with cryptorchidism concluded that the infertility and cancer risk associated with undescended testes result from hormonal deficiency during development, not from temperature-induced cell damage.¹⁴

This distinction matters because it means cooling the scrotum is not a treatment for every fertility problem, even when the problem involves the testes. Temperature sensitivity is real and well-documented for mature spermatogenesis, but some conditions that look like they should respond to temperature management actually have different underlying causes. A fertility evaluation from a urologist or reproductive endocrinologist will do more good than any DIY cooling protocol for men who have not had their specific situation diagnosed.

Why Testes Ended Up Outside the Body

The evolutionary question of why mammalian testes are external is more contested than you might expect. The straightforward answer, that sperm need cooler temperatures, is true but probably not the whole story. One hypothesis proposes that testicular externalization evolved alongside the rise of endothermy (warm-bloodedness) in the mammalian lineage, as internal body temperatures climbed above the threshold that sperm production could tolerate.¹⁵ The scrotum may have appeared before modern mammals diverged, and some lineages later lost it when they evolved alternative ways to handle the heat problem (elephants and some marine mammals, for instance, keep their testes internal but have specialized vascular cooling systems).

A more recent proposal adds a testosterone-regulation angle. External testes produce less testosterone than they would at core body temperature, because the enzyme pathway driving androgen production is temperature-sensitive. One researcher has argued that this is not a bug but a feature: exteriorizing the testes tempered testosterone production and helped avoid excessive masculinization of male offspring, which could have been harmful during mammalian evolution.¹⁰ A broader review concluded that multiple selection pressures, not just sperm protection, likely shaped the current diversity of testicular positions across mammalian species.¹⁶

None of this evolutionary background changes the practical advice, but it adds useful context. The temperature sensitivity of your testes is not a design flaw to be hacked with ice packs. It is a deeply embedded feature of mammalian biology, one your body has elaborate systems to manage. Scrotal cooling interventions work best understood as supplements to those systems when they are overwhelmed by modern conditions (prolonged sitting, tight clothing, hot work environments), not as upgrades to a system that is otherwise running fine.

What the Sleep Data Shows

One genuinely surprising finding from the scrotal cooling research is where the thermal damage happens. When researchers monitored 24-hour scrotal temperature profiles, they found that in men with poor sperm quality, the highest scrotal temperatures were consistently recorded during rest and sleep, not during physical activity. The lowest temperatures were measured during periods of movement or frequent position changes.⁶ Compared to men with normal semen quality, the infertile men spent significantly more time with scrotal temperatures above 35.5°C, even in the same ambient conditions.

This flips the intuitive picture. Many men worry about hot showers, saunas, or exercise, but the sustained, low-grade warming that happens when you sleep in heavy bedding, in warm pajamas, or on your stomach may accumulate more thermal damage simply because it lasts longer. The scrotal cooling studies that showed the biggest fertility improvements specifically targeted nighttime for exactly this reason. If you are trying to reduce scrotal heat exposure for fertility purposes, lighter bedding and looser sleepwear at night may be more impactful than brief daytime cooling rituals.