Men with an enlarged prostate should not take medications that contain antihistamines or decongestants. These agents are often found in over-the-counter cold, sinus, and allergy medications.

To understand why, it helps to review some prostate anatomy. The prostate is a walnut-sized gland that produces seminal fluid. This fluid mixes with sperm to form ejaculate – the semen that is expelled from the penis when a man reaches orgasm.

Running through the prostate is the urethra – the tube from which urine and semen exit the body.

As men get older, it’s common for the prostate gland to grow inward. This results in an enlarged prostate or benign prostatic hyperplasia (BPH). Scientists aren’t sure why this happens. In some cases, the prostate itself does not enlarge, but it undergoes changes which make it more sensitive to chemicals that your body naturally produces. 

The prostate may also undergo other changes which may slow down the flow of urine or increase urinary symptoms such as frequency and urgency. 

Because of these changes, many men experience trouble emptying the bladder, find that they have to use the bathroom more often (especially at night), or feel a greater urge to urinate.

Antihistamines and decongestants may add to the problem. These drugs can make it harder for the prostate and the bladder to relax, making it even more difficult for urine to flow.

Fortunately, there are other ways to treat colds and allergies. Men with BPH should talk to their doctors about the treatments that are right for them.