December 2025

During cold and flu season, you may reach for over-the-counter (OTC) cough and cold medicines to manage symptoms. However, these medications can sometimes cause unpleasant side effects. Here’s what to expect and how to feel better.

Drowsiness

Respiratory viruses can often cause fatigue, and certain medications can worsen this condition.

Take any medications with a “may cause drowsiness” or “nighttime” label before bed to allow them to take effect. If you’re feeling drowsy, take a nap during the day, and get a good night’s sleep. Rest helps you recover and strengthens your immune system.

Upset stomach

Whenever you start a new medicine, it can cause nausea. Unless directed otherwise, take your medicine with bland food, such as crackers, potatoes, plain toast, or rice.

Dry mouth, nose, or throat

Your body can lose fluids from coughing and blowing your nose. Decongestant medicines used to relieve a stuffy nose can also cause dehydration.

To stay well hydrated, the National Library of Medicine (NLM) recommends caffeine-free fluids, fresh fruits, vegetables, and soup. This approach helps thin your mucus, making it easier to clear through coughing or blowing your nose.

To relieve dry mouths or nasal passages, the Mayo Clinic recommends using a cool-mist vaporizer or humidifier in your home. Saline nasal sprays can also help.

Constipation

With dehydration comes constipation, especially for older adults. Prevent constipation by incorporating more fiber into your diet through beans or leafy greens, such as adding kale or escarole to your chicken soup. Harvard Health also recommends taking a fiber supplement with psyllium seed or methylcellulose. If those options bother your stomach, try a supplement with guar fiber instead.

Side effects in children

OTC cough and cold medicines can have dangerous and even fatal side effects for babies and young children. The American Academy of Pediatrics recommends avoiding these medications for children younger than four years of age. For children between the ages of 4 and 6, these medicines should only be given as directed by a doctor. For older children, follow label directions.

When to call your doctor

For most people, OTC cold and flu medicines are safe to use if you follow the label directions and dosing. The NLM recommends calling your doctor if you develop a rash or if any of these side effects are severe, get worse, or do not go away:

• Dizziness or lightheadedness.
• Drowsiness.
• Nervousness or restlessness.
• Nausea or vomiting.
• Stomach pain.

How your pharmacist can help

Before starting any new OTC medication, you can ask your pharmacist for a medication review. This review can help you know what side effects to expect, how to manage them, and when to call your doctor. Your pharmacist can also:

• Help choose a cold and flu medicine based on your symptoms. Taking medications you don’t need can cause side effects.
• Make sure any OTC medicines are safe for your existing health conditions. According to the American Heart Association, decongestants — medications with pseudoephedrine or phenylephrine — can increase blood pressure.
• Check for interactions with other medicines you take. These can make side effects worse.
• Make sure you don’t take too much of the same active ingredient, especially acetaminophen. This medication is often found in OTC and prescription painkillers and in multi-symptom cough and cold medicines. Taking too much acetaminophen can cause liver damage or failure.