Antihistamines are a go-to treatment for allergies, hayfever, and sometimes sleep issues. Millions of men take them regularly, often without thinking twice. However, if you’re trying to conceive, a surprising question may be worth asking, could antihistamines be affecting your fertility?
At present, the science isn’t definitive. However, there are emerging concerns from animal studies and a small number of human reports that suggest a potential link between regular antihistamine use and male fertility problems, particularly in sperm production and motility.
In the UK, general practitioners (GPs) receive minimal training in male fertility and may not be aware of this potential connection. So, if you’ve been trying for a baby and are also a regular antihistamine user, here’s what the current science says and what you can do.
What are Antihistamines, and why do we take them?
Antihistamines are medications that block the action of histamine, a chemical your body releases during allergic reactions. There are two main types:
- First-generation antihistamines (e.g., diphenhydramine, chlorphenamine): Cross the blood-brain barrier; often sedating.
- Second-generation antihistamines (e.g., cetirizine, loratadine, fexofenadine): More selective; generally non-drowsy.
They’re commonly used to treat hay fever, eczema, hives, allergic rhinitis, and insect bites. Some sleep aids also contain first-generation antihistamines due to their sedative effects.
Limited but concerning evidence
While large-scale human trials are lacking, existing research mainly in animals raises valid concerns.
Animal studies
- A 2018 study in rats found that long-term use of diphenhydramine and cimetidine (an H2 blocker) resulted in reduced sperm count, poor motility, and structural changes in the testes.
- Histamine plays a known role in spermatogenesis (sperm production) and testicular hormone regulation. Blocking histamine receptors could interfere with this process.
Human study: Hayashi et al. (2006)
One of the few human studies available, conducted in Japan, investigated asthenozoospermia (low sperm motility) in men with hay fever. The researchers found that men taking histamine H1 receptor antagonists (common antihistamines) showed improved sperm motility after discontinuing these medications.
This suggests a reversible relationship between antihistamine use and reduced fertility in some men. However, it must be noted that the sample size was small, and more research is needed.
Histamine may play a role in Testosterone production
Histamine receptors are found in Leydig cells, which are responsible for testosterone production in the testes. Some researchers hypothesise that antihistamines could impact testosterone levels indirectly, though human data is lacking.
Why your GP may not know about this
In the UK, male fertility is underrepresented in both public health discourse and medical training. General practitioners:
- Rarely receive specialised training in male reproductive health.
- Are unlikely to link routine medications like antihistamines with fertility unless prompted.
- May focus more on female partners during fertility assessments as much more training in gynaecology is provided during medical studies and the public opinion is putting much more emphasis on women’s health.
If you're using antihistamines regularly, you may need tadvocate for yourself to get these issues explored.
What we still don’t know (yet)
Despite some warning signs, major gaps in knowledge remain:
- We don’t yet have large, controlled clinical trials assessing antihistamines and sperm health in humans.
- It’s unclear whether second-generation antihistamines are safer than first-generation ones.
- The duration and dose of use required to trigger fertility effects are still unknown.
- The precise mechanism of action and how antihistamines may interfere with testicular function is not well understood.
Until these questions are answered, the link between antihistamines and male fertility remains possible but unproven.
What you can do today: Practical advice
If you're trying to conceive and regularly using antihistamines, here are some common-sense steps to consider:
1. Review your medications
Check if you’re taking any medications, prescription or over the counter, that may contain antihistamines, especially:
- Allergy tablets
- Sleep aids (many contain diphenhydramine)
- Cold and flu remedies
If you are considering changing or stopping medication then this should be discussed with your GP or doctor.
2. Try non-drug allergy relief (under medical guidance)
Consider alternatives for managing allergies:
- Use saline nasal sprays or a nasal rinse
- Install HEPA filters in your bedroom
- Keep windows closed and avoid going out during high pollen seasons
- Shower after being outdoors to remove allergens
3. Switch antihistamines (under medical guidance)
Ask your GP or pharmacist if you can switch to a second-generation antihistamine or use them only on an “as-needed” basis rather than daily.
4. Get a semen analysis
If you’ve been trying to conceive for over 6–12 months, a semen test can provide key insights into your fertility. If abnormalities are found, you should discuss this with an andrologically qualified urologist. Antihistamines may be a factor to consider.
5. Optimise your reproductive health
Medications are just one piece of the puzzle and antihistamines are an even smaller part of that puzzle. It’s important to also focus on other aspects of your lifestyle and diet to ensure you’re doing all you can to improve all areas of your health and fertility. This includes:
- Quit smoking
- Limit alcohol
- Maintain a healthy BMI
- Sleep well and reduce stress
Along with all the other general health and fertility guidance that is suggested to improve sperm health.
The bottom Line
While there’s no definitive evidence that antihistamines cause male infertility, there’s enough biological plausibility and preliminary data to take a cautious, informed approach, especially if you're struggling to conceive without an obvious cause.
In the UK, this topic is often under-recognised by healthcare professionals, meaning that you may need to advocate for your self and raise questions proactively.
Still concerned?
If you’re using antihistamines regularly and trying to conceive, speak to a fertility specialist or a GP with an interest in men’s health. Even if your doctor hasn’t encountered this issue before, bringing the emerging research to their attention could make a difference in your care.
References
- NICE Guidelines on Fertility (2020); www.nice.org.uk
- Hayashi T, Yoshida S, Ohno R, Ishii N, Terao T, Yamada T (2006); Asthenospermia in hay fever patients improved by stopping treatment with histamine H1 receptor antagonists. Int J Urol 13(7): 1028-1030.
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