Antihistamines, especially older sedating types, should be avoided due to significant side effects like drowsiness, impaired coordination, dry mouth, and confusion, which increase accident risks and mask serious conditions like anaphylaxis, with newer non-sedating options generally safer but still requiring caution for conditions like glaucoma, heart disease, or prostate issues, and never used for cough/cold in young children.
Like all medicines, antihistamines can cause side effects. Side effects of antihistamines that make you drowsy can include: sleepiness (drowsiness) and reduced co-ordination, reaction speed and judgement – do not drive or use machinery after taking these antihistamines.
For allergies during pregnancy, cetirizine (Zyrtec) and loratadine (Claritin) are generally considered the first-choice antihistamines due to established safety profiles, while older options like chlorpheniramine are also recommended, especially in the first trimester; always use the lowest effective dose and consult your doctor before taking any medication.
Side effects of H2 (digestive) antihistamines are uncommon but can include: Fatigue. Diarrhea or constipation. Joint or muscle pain.
Yes, antihistamines can cause headaches, which for some people might manifest as or trigger migraines, though headaches are a common side effect of both older (sedating) and newer (non-sedating) types, notes GoodRx and Healthdirect. While antihistamines can help with allergy-related headaches, the medication itself can sometimes induce head pain or be linked to migraine pathways, with some studies suggesting histamine's role in migraine mechanisms, say researchers from MDPI and Springer Nature.
CONCLUSIONS. The first-generation antihistamines negatively affect mood, sleepiness, alertness, and cognitive and psychomotor functioning in adults and children. As a result, these medications can interfere with performance and safety, even when taken the night before.
The "5 C's" commonly cited as potential migraine triggers are Cheese, Chocolate, Coffee, Cola (and other caffeinated drinks), and Citrus fruits, often due to compounds like tyramine or caffeine they contain. However, these triggers aren't universal; many people experience migraines from other factors like stress, lack of sleep, or skipped meals, so keeping a migraine diary to identify personal triggers is key, notes Headaches Australia and the American Migraine Foundation.
Symptoms of a Histamine Dump at Night
Skin Reactions: Itching, hives, rashes, or flushing may occur due to histamine's effects on the skin. Nasal Congestion or Sinus Issues: Histamine can cause swelling in the nasal passages, leading to congestion or a runny nose.
Older adults should ideally use second-generation antihistamines (like cetirizine, loratadine, or fexofenadine) as they are less likely to cause drowsiness and cognitive impairment compared to first-generation antihistamines.
H1 first-generation antihistamines: Common adverse effects include sedation, cognitive impairment, and anticholinergic adverse effects such as dry mouth, urinary retention, constipation, and blurred vision. Dizziness, tinnitus, and delirium may occur at high doses.
There's no evidence to suggest that taking cetirizine will reduce fertility in either men or women. Speak to a pharmacist or your doctor before taking it if you're trying to get pregnant.
Pregnancy rhinitis is a stuffy or blocked nose during pregnancy that's not caused by allergies or a cold. You might also have a runny nose, sneezing and nasal swelling. Pregnancy rhinitis usually happens in your third trimester and can last until two weeks after you deliver.
Antihistamines, which are commonly used to treat symptoms such as a runny nose or sneezing, are generally safe for patients with abnormal heart conditions. However, the FDA has warned that antihistamines taken in conjunction with some high blood pressure medications may cause a spike in blood pressure.
If you're using oral antihistamines very often, you might have wondered if it's OK to keep relying on antihistamines to control symptoms of allergies. The good news is there's no research evidence to suggest regular, long-term use of modern antihistamines is a problem.
Anxiety caused by antihistamines should go away once you stop taking the medication. If you notice you feel more nervous in the hours following a dose of these allergy medications, speak with your provider about alternatives.
Be aware, too, that first-generation antihistamines typically are not recommended for adults 65 and older. That's because they have something called anticholinergic properties. Research suggests those properties might raise the risk of dementia.
Non-drowsy options like loratadine and cetirizine are among the safest choices for long-term allergy relief. Both medications work by blocking the effects of histamine, and people generally tolerate them well.
These are some examples of prescription allergy medicines:
Excess histamine can cause a variety of different symptoms which very often mimic allergic reactions. The most common symptoms are rashes (e.g. hives), itching, flushing, irritable bowel syndrome (IBS), indigestion, breathlessness, palpitations, migraines, dizziness, anxiety/panic, joint aches and nasal congestion.
Histamine levels are another potent downstream target. Allergic symptoms exacerbate during nighttime and plasma histamine levels exhibit nocturnal peaks. In mastocytosis patients, peak levels of plasma histamine were observed in the early morning with the lowest in the afternoon (19).
Medical Conditions
Autoimmune disorders affect immune system function, which might lead to more histamine being released (11). Another condition causing elevated histamine levels is mastocytosis, rare disorder involving abnormal mast cell growth—the cells that make and store histamine (12).
Bananas: High in magnesium, bananas are a great source for a quick energy boost and can help reduce hunger headaches. Berries: Due to their high antioxidant content, blueberries, strawberries and blackberries can help relieve headaches caused by sinus pressure and brain inflammation from stress.
Apply hot or cold compresses to your head or neck. Ice packs have a numbing effect, which may dull the pain. Hot packs and heating pads can relax tense muscles. Warm showers or baths may have a similar effect.
Stress. Stress is one of the most common triggers among people with migraine.