When choosing an antihistamine or trying to determine where a new symptom is coming from, be aware that the medication can cause side effects, some of which may be a little surprising. Here are some of the most common antihistamine side effects you should know about.
Drowsiness or drowsiness is one of the most common side effects of antihistamines, especially when it comes to first generation antihistamines. It is so common, in fact, that diphenhydramine is actually used as a sleeping pill in certain medications. This side effect is obviously not terrible if you have to drive or use heavy machinery after taking your allergy medication, but Dr Lane says it may be beneficial in other circumstances, such as if your symptoms are severe. Allergy make it difficult for you to get to sleep at night. Just be aware that it can also cause dizziness in the morning, he says.
However, if this starts to become a regular problem, you may want to discuss other options with your doctor. Having serious sleep problems or having allergies every night probably warrants a better strategy for managing insomnia or allergies.
Newer antihistamines tend not to sedate as much, but they still can in some people, says Dr. Lane. In his experience, Zyrtec has the highest incidence of sedation, followed by Xyzal, Claritin and Allegra, respectively.
2. Dry mouth
Another very common side effect of antihistamines is dryness, especially dry mouth, says Dr. Lane. Again, this is most common with older drugs, but can occur with newer ones as well. The current thought is that it is the effects on acetylcholine that cause this side effect, which is why it is more common with first generation drugs.
This particular side effect is usually not serious, but if you are trying to manage dry mouth for other reasons, be aware that your antihistamine may be helping it.
3. Dry eyes
Similar to dry mouth, dry eye is also a common side effect of antihistamines. It is believed that some antihistamines may actually reduce your tear production via acetylcholine-related effects, which makes your eyes drier. This is especially annoying because dry eyes can also be red, itchy, and itchy, which are also common symptoms of itchy eyes from allergies. Further drying out allergic eyes can sometimes make symptoms worse.
Yes, antihistamines can have an effect on your bowel habits too! Again, this is due to the effects of the drugs on acetylcholine signaling. Normally, this neurotransmitter plays a role in controlling your gut muscles, which help get things done. If this movement is slowed down by a drug that interferes with acetylcholine, you may be a little constipated. But, as with other side effects associated with acetylcholine, it is more common with first generation antihistamines than second generation antihistamines.
5. Urinary retention
Increased urinary retention, which means your bladder doesn’t empty completely when you pee, is another possible side effect of antihistamines that is linked to their actions on acetylcholine. In the same way that drugs can affect the muscles of the intestines, they may also affect the muscles of the bladder, which makes it difficult to completely empty the bladder.
6. Dry skin
While not as common as dry mouth or eyes, dryness affecting your skin can be a side effect of antihistamines, says Dr. Lane. In general, however, dry skin is affected more directly by other factors, such as weather changes or your environment.
7. Tolerance (sort of)
If you feel like the antihistamines you are taking are not working as well as they used to be, you are not alone. Experts are not sure exactly what is causing this problem (whether we really do develop a true tolerance to the drug or if our symptoms get worse, for example), but it is a problem that allergists see frequently, Dr. Lane said.
Fortunately, if you’re using over-the-counter medications, this problem has a pretty simple fix: move on! In fact, Dr Lane says some people are able to switch to another drug for a while and then revert to their old sleep mode a few months or years later if they start having problems with the new one. So this problem is not always permanent, he says.
8. Reduced lubrication
It’s not one of the more common antihistamine side effects, but reduced vaginal lubrication is a possibility, SELF explained previously. Vaginal dryness is a known side effect of anticholinergic drugs, including antihistamines with anticholinergic effects, as these drugs can cause blood flow changes that dry up the mucous membranes in the body.