Can antihistamines (anti-histamine medications) increase blood pressure (hypertension)?

Can Antihistamines Increase Blood Pressure?

Antihistamines themselves do not increase blood pressure; however, many over-the-counter antihistamine products contain decongestants (pseudoephedrine or phenylephrine) that can elevate blood pressure, which is the primary concern in hypertensive patients. 1

Key Distinction: Antihistamines vs. Combination Products

Pure Antihistamines (Safe for Blood Pressure)

• Second-generation antihistamines (cetirizine, fexofenadine, loratadine, desloratadine) do not elevate blood pressure and are preferred for patients with hypertension due to their lack of cardiovascular effects 1, 2
• First-generation antihistamines (diphenhydramine, hydroxyzine, chlorpheniramine) also do not directly increase blood pressure, though they carry other risks including sedation and anticholinergic effects 1
• The 2017 ACC/AHA Hypertension Guidelines specifically recommend intranasal corticosteroids and antihistamines as alternative therapies to decongestants for patients with hypertension who need treatment for nasal congestion 1

Decongestants (The Actual Problem)

• Oral decongestants (pseudoephedrine, phenylephrine) can elevate blood pressure through alpha-adrenergic receptor stimulation 1, 3
• The 2008 AAAAI guidelines state that "elevation of blood pressure after taking an oral decongestant is very rarely noted in normotensive patients and only occasionally in patients with controlled hypertension," but recommend monitoring hypertensive patients due to interindividual variation 1
• Pseudoephedrine stimulates both alpha and beta receptors, elevating blood pressure with an increase or no change in heart rate, while phenylephrine stimulates alpha-adrenergic receptors, causing blood pressure elevation with reflex bradycardia 3

Clinical Management Algorithm

For Patients With Hypertension Needing Allergy/Cold Relief:

1. First-line: Use pure antihistamines without decongestants

   • Recommend second-generation antihistamines (fexofenadine, cetirizine, loratadine) as they have no blood pressure effects and minimal sedation 1, 2
   • Intranasal antihistamines are also appropriate alternatives 1, 2

2. For nasal congestion specifically:

   • Use intranasal corticosteroids as first-line therapy (most effective for all four major rhinitis symptoms without blood pressure effects) 1
   • Consider short-term topical decongestants (≤3 days) to avoid rhinitis medicamentosa 1

3. If oral decongestants are necessary:

   • Use only in patients with controlled hypertension 1
   • Monitor blood pressure closely due to unpredictable individual responses 1
   • The 2020 ISH guidelines note NSAIDs can increase blood pressure by up to 3/1 mm Hg, and sympathomimetics (including decongestants) are listed as blood pressure exacerbators 1

4. Avoid entirely in:

   • Patients with uncontrolled or severe hypertension 1
   • Elderly patients (more sensitive to adverse effects) 1

Important Caveats

• The confusion arises because combination cold/allergy products often contain both antihistamines AND decongestants - patients and providers must read labels carefully 1, 3
• First-generation antihistamines with anticholinergic effects raise concerns in patients with mast cell activation syndrome who are prone to cardiovascular events, but this relates to tachycardia and cardiovascular instability, not hypertension per se 1
• NSAIDs (often taken concurrently for cold symptoms) can increase blood pressure by an average of 5 mm Hg, which is a separate and more significant concern than antihistamines 1
• The 2017 ACC/AHA guidelines explicitly list decongestants as substances to avoid or use with caution, while antihistamines are recommended as safer alternatives 1