Flu Season and Immune Protection During Travel: What Works, What Doesn’t, and How to Stay Well

1. Why Immune Health Matters During Travel

Air travel and crowded spaces during flu season make the perfect storm for winter misery. Airplane cabins recycle air with low humidity, which dries the nasal passages and impairs your body’s first line of defense. Add in disrupted sleep, stress of travel, new time zones, and close contact with others, and it’s easy to understand why so many travelers come home sick.

The immune system does its best work under stable conditions: consistent sleep, balanced meals, and low stress. Travel disrupts all three. Preparing your body in advance and using a few evidence-based tools can reduce the duration and severity of illness, even if you can’t prevent every exposure.

And YES! all off these strategies can be used when you're at home too! Respiratory viruses run rampant in offices, schools and daycares too! If you have adorable little fomites who are prone to bringing home germs, this article is just as relevant.

2. How Travel Challenges the Immune System

Your immune system operates on two levels: innate immunity (the rapid first response) and adaptive immunity (the memory-based defense built after exposure). Travel-related stress can suppress both. Research shows that sleep deprivation and circadian disruption reduce white blood cell activity and antibody responses (1).

Flying across time zones alters cortisol and melatonin rhythms, which weakens immune vigilance. Dehydration from cabin air adds another layer of risk because dry mucous membranes allow viruses to enter more easily. Diet changes and disrupted gut microbiota during travel can also impair the mucosal immune barrier, your body’s largest interface with the outside world.

3. Core Prevention Strategies Before You Pack a Supplement

Before diving into pills and sprays, the foundation of immune protection is simple:

• Vaccinate early. Get your flu shot and COVID booster at least two to four weeks before travel for peak antibody response (2).
• Prioritize rest. Sleep deprivation decreases natural killer cell activity, a key antiviral defense.
• Stay hydrated. Aim for 1 liter of water every four hours of flight time.
• Protect nasal moisture. Use saline spray or gels to maintain mucosal integrity.
• Mask selectively. In crowded airports or during flu surges, masking still reduces transmission.
• Eat protein-rich meals. Protein fuels immune cells and supports recovery.

These habits strengthen the terrain so that supplements can work more effectively.

4. Elderberry: Start Before Symptoms During Travel

Elderberry (Sambucus nigra) has gained attention for its antiviral and anti-inflammatory effects. The key compounds, anthocyanins and flavonoids, are thought to block viral attachment and support cytokine balance.

The best evidence for travelers comes from a randomized, double-blind, placebo-controlled trial involving long-haul air passengers. Participants began taking 600 mg of standardized elderberry extract daily 10 days before travel, increased to 900 mg per day starting one day before departure, and continued through four to five days after arrival. Those taking elderberry had significantly shorter cold duration and milder symptoms, and infection rates were lower in the elderberry takers (3).

For those who are already sick, other clinical trials show benefits when elderberry is started at symptom onset. One study found that 15 mL of elderberry syrup four times daily for five days shortened recovery from influenza by about four days compared with placebo (4).

Safety notes: Avoid raw or unprocessed elderberries, as they contain cyanogenic compounds. Data are limited for pregnancy and breastfeeding, so discuss use with your healthcare provider. People with autoimmune conditions should also consult a clinician before use (5).

See the table below for the optimal effective dosage elderberry.

5. Azelastine Nasal Spray: An Unexpected Ally Against COVID

Azelastine is an antihistamine nasal spray approved for allergic rhinitis, but emerging research suggests it may also reduce viral replication in nasal tissue. Laboratory and small clinical studies show azelastine inhibits SARS-CoV-2 entry into nasal epithelial cells by stabilizing cell membranes and reducing viral adhesion (6,7).

For travelers, azelastine can help maintain nasal integrity and reduce congestion, potentially lowering the risk of viral transmission. The standard dosage is one to two sprays per nostril twice daily.

Pro Tip: Make sure you’re spraying into the nasal turbinates and not straight up the nostrils. It is safe for regular use and has minimal systemic absorption. However, it should not replace vaccines or medical treatment for active infection.

As an alternative, saline nasal sprays and gels can also protect nasal mucosal integrity and help prevent viral transmission.

6. Zinc: Use Early and Use Moderately

Zinc supports immune cell signaling and mucosal defense. A meta-analysis of randomized trials found that zinc lozenges can shorten the duration of the common cold by one to two days when started within 24 hours of symptom onset (8).

The most effective forms appear to be zinc acetate and zinc gluconate lozenges. For prevention during travel, 15–30 mg of elemental zinc daily is sufficient. During active illness, short courses up to 40 mg per day for 3–7 days may be used. Taking too much zinc for extended periods can cause nausea and interfere with copper absorption, so moderation matters.

7. Vitamin C: Helpful, But evidence is not great