After reading some studies around heat and sperm health I bought these. Three months later my metrics were looking significantly better and I feel more energised. Wish I'd found these sooner.
We'd been trying for a while with no luck. Then I changed to BULLS, made a few other lifestyle tweaks and we got some amazing news a few weeks ago. These are now a staple of my health routine - I wouldn't go without them.
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Sperm counts have dropped 51% since 1973. Your underwear & environment is part of the problem.
The average man today has half the sperm count of his grandfather. Scientists have identified heat, synthetic materials, and environmental toxins as key drivers - and most men are exposed to all three before they leave the house.
BULLS was created because the science is clear - maintaining optimal scrotal temperature and wearing natural materials are associated with healthier sperm quality and testosterone levels.
Time to put the power back in your BULLS. 🐂
Don't just take our word for it 🐂
Honestly bought these half for the health angle and half out of curiosity. What I didn't expect was how much better they feel than anything else I've worn. The fit is proper, comfortable and can happily wear daily. Peace of mind on the health angle also, bought a few pairs, thanks lads!
As a frequent sauna user, Bryan Johnson's findings on heat and sperm health were concerning. BULLS give me the peace of mind to enjoy the sauna and its benefits without worrying. I also feel like I can last longer in the sauna which is great.
I'm 31, no kids planned yet, but I take my health seriously. When I read about sperm count decline and microplastics I started looking at everything - my diet, my training, my sleep. Switching to BULLS was a no-brainer. They're genuinely the most comfortable boxers I've owned and I don't have to think about what they're doing to my body.
I'm into optimising everything (a bit freakishly but f*ck it, I'd rather be healthy) training, sleep, nutrition. When I learned that scrotal temperature directly affects testosterone levels, not just fertility, I took it seriously. I've been wearing BULLS for two months alongside getting my bloods done regularly. My total T has gone up. I'm not claiming it's one thing, but I've changed very little else. These are now just part of the stack.
My wife and I had been trying for a while with no luck. My GP mentioned heat as a factor so I started looking into it properly. Changed my underwear to BULLS, made a few other lifestyle changes, and a few months later we got some great news. I can't say it was only the boxers but I'm definitely keeping them in my routine. We'll be trying for a second soon enough!
BULLS 🐂 vs Other Brands
We built BULLS around the science of male wellbeing. Most underwear brands never did. 🐂
Support Healthy Sperm Quality
Support Optimal Testosterone Conditions
95% Cotton For Wellbeing
Science Backed & UK Brand
BULLS 🐂
Other Brands
Support Healthy Sperm Quality
Support Optimal Testosterone Conditions
95% Cotton For Wellbeing
Designed For Male Wellbeing
FAQ's
How is this different from regular boxers?
Most underwear is made from synthetic fabrics like polyester and nylon - materials that trap heat, shed microplastics, and sit against your most sensitive skin all day. BULLS are engineered specifically for male biology. The cotton body supports temperature regulation, allows airflow, and contains zero synthetic fibres. Regular boxers were designed for maximising profit. BULLS were designed for your wellbeing and performance.
Can BULLS support my sperm health?
We won't make promises a pair of boxers can't keep. What we will tell you is this: peer-reviewed research consistently shows that scrotal temperature has a direct impact on sperm quality, motility and testosterone levels. The testes sit outside the body for a reason - they need to stay cooler than core body temperature to support healthy sperm production. Synthetic underwear works against that. BULLS works with it - a cotton body and cooling patch designed to support scrotal temperature regulation. Combined with a healthy lifestyle, switching your underwear is one of the simplest and most evidence-based changes you can make.
What are they made of?
BULLS Performance Boxers are 95% natural cotton, 5% elastane.
The cotton does the heavy lifting - no microplastics, no synthetic fibres, nothing associated with the heat retention or hormonal disruption linked to conventional synthetic fabrics. The 5% elastane is there purely for fit, stretch and longevity of the boxer, and while we won't pretend it isn't present, it's a fraction of what you'll find in conventional underwear.
The average polyester boxer brief is 80-100% synthetic. BULLS is 95% natural.
That's not a perfect solution - we'll be honest about that. Our goal is fully natural materials as the brand grows. But right now, 95% natural cotton is a significant upgrade over what most men wear every day, and the science on microplastic harm relates specifically to high-concentration synthetic fabrics like polyester and nylon - not trace elastane in a predominantly natural garment.
Better isn't always perfect. But better is still 95% better. 🐂
How long until I notice a difference?
Sperm take approximately 74 days to fully mature - that's biology, not a limitation of the product. This means any meaningful change in sperm quality takes roughly 10-12 weeks to show up in a semen analysis. For best results, we recommend consistent daily wear alongside a healthy lifestyle.
Do they work if I'm not actively trying for a baby?
This is the question we get most and the honest answer is that most BULLS customers aren't trying to conceive right now. Sperm count and testosterone are linked to far more than fertility. Energy levels, mood, drive, physical performance these are all downstream of male reproductive health. The same conditions that reduce sperm count also suppress testosterone. If you train hard, take your health seriously, and want your biology working for you rather than against you, BULLS aren't a fertility product. They're a performance choice.
What's your return policy?
If you're not satisfied within 30 days of receiving your order, we'll make it right - no awkward returns process, no questions that make you feel like the problem. We stand behind the product because we believe in it. Reach out to our team directly and we'll sort it.
hello@bullsmission.com
How does everyday heat and sauna affect sperm health?
Your testes operate 2-4°C below core body temperature for a reason - that precise cooling is what makes healthy sperm production possible. When that temperature rises, even slightly, sperm quality, motility, and morphology can all be affected. Everyday factors like synthetic underwear, sitting for long periods, and laptops on your lap contribute to this constantly.
Saunas are a more dramatic example. Biohacker Bryan Johnson documented this precisely: sauna sessions without scrotal cooling produced a 54% drop in motile count, a 57% drop in motility, and a 55% drop in normal morphology. The same sessions with active cooling told a completely different story - 27 daily sauna sessions with ice on the balls saw total motile count up 57%, concentration up 26%, motility up 16%, and normal morphology up 15%.
The lesson isn't to avoid sauna - it's to manage the heat your body is exposed to the rest of the time. BULLS are designed around exactly that principle. Support consistent temperature regulation and give your biology the conditions the science associates with optimal male health.
How do I wash them?
Pop them in wash as you usually would any cotton pair of boxers.
Do you ship worldwide?
Yes we do.
Every day in the wrong underwear & conditions is a day inside a 74-day sperm cycle you can't redo.
Sperm take 74 days to mature. The ones forming right now are being shaped by the heat, synthetics, and toxins you're exposed to today. Not last month. Today.