Open Source Apothecary At Home / The twelve-month course

Unit 9 (September): Immune, respiratory, and the honest cold season

The month with the most nonsense sold and the least that actually works — honey, sleep, and one genuinely useful berry.

guide

The physiology. Immunity is two systems: innate (fast, non-specific — barriers, phagocytes, inflammation) and adaptive (slow, specific — antibodies and memory). Vaccination works by training the adaptive system. "Boosting" immunity has no defined biological meaning, which is the single most useful thing to know before spending money this month.

What actually works, in order of effect size.

1. Sleep. Short sleep is associated with increased infection risk and reduced vaccine response. 2. Vaccination, where one exists for the pathogen in question. 3. Vitamin D in people who are deficient — the benefit is concentrated in the deficient, and correcting a deficiency is reasonable. 4. Zinc, started within 24 hours of a cold starting, shortens it modestly. Long-term high-dose zinc causes copper deficiency. 5. Honey for cough — better trial evidence than most cough medicines, and absolutely not under 12 months of age. 6. Elderberry — small trials for influenza-like illness, modest, some industry-funded. Adjunct, not a substitute for vaccination or antivirals.

What does not work. Echinacea's trials are inconsistent and the effect, where present, is small. Vitamin C taken at the onset of a cold does not work; prolonged supplementation has a marginal effect in people under extreme physical stress. Garlic has small trials with inconsistent results. Most of the immune-support market has no evidence of reducing illness.

The red flags matter most in this system, because a chest infection and a cold look similar at the start and differ enormously by day three.

What the studies found

Growing it

In season

• Elderberry — berries fully dark; harvest whole umbels
• Echinacea — aerial parts at full flower; the root waits until autumn
• Thyme — cut and dry now for the winter cough blend
• Sage — cut back after flowering; dry for gargles
• Mullein — leaves from rosettes; flowers for ear oil

Garden work

• Harvest and dry the respiratory herbs while the weather allows
• Cook elderberries. Never use green ones.
• Keep drying: shade for the aromatics, and keep the air moving

Preparation

Project: elderberry syrup and a cough blend

Elderberry syrup

• Ripe, dark berries only — simmer with water until soft, mash, strain
• Add honey only after the liquid is off the heat
• Do not give honey-based syrup to infants under 12 months
• Refrigerate; keeps a few weeks

Cough blend

• Thyme, marshmallow and mullein, with a little licorice for taste
• Take marshmallow as a cold infusion — heat degrades the mucilage
• Honey alone does most of the work for cough, and it is the best-evidenced element

Sage gargle for sore throat

• 1-2 g dried sage in 250 mL just-boiled water, 10 minutes, strained, pinch of salt
• Cool to comfortably warm, gargle, spit. Do not swallow.

Zinc, if using it

• Start within 24 hours of symptom onset, short course only
• Long-term high-dose zinc causes copper deficiency.

Cautions and interactions

• No honey under 12 months of age — infant botulism.
• Elderberries must be ripe and cooked.
• Long-term high-dose zinc causes copper deficiency.
• Do not use echinacea in autoimmune disease or with immunosuppressants.
• St John's wort must not be combined with an SSRI.
• Most immune-support products have no evidence of reducing illness.

When this is not a self-care problem — get help

• Breathlessness, chest pain, coughing blood, or a cough lasting over three weeks — medical assessment.
• Fever with a productive cough and feeling very unwell — possible pneumonia; urgent assessment.
• A sore throat with difficulty swallowing saliva, drooling or breathing difficulty — emergency care.
• A fever in an infant under three months — emergency assessment.

Related

• The twelve-month course
• "Immune support": what the trials actually show
• Coughs and colds: honey, zinc, and the honest list
• Influenza and when it is serious
• Elderberry
• Sore throat

Sources

1. Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of stratified aggregate data. The lancet. Diabetes & endocrinology 2025; doi:10.1002/9781119536604 PubMed 39993397
2. Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials. The lancet. Diabetes & endocrinology 2021; doi:10.1016/S2213-8587(21)00051-6 PubMed 33798465
3. Effect of micronutrient supplements on influenza and other respiratory tract infections among adults: a systematic review and meta-analysis. BMJ global health 2021; doi:10.1101/2020.04.08.20058578 PubMed 33472840
4. Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials. Complementary therapies in medicine 2019; doi:10.1016/j.ctim.2018.12.004 PubMed 30670267
5. Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis. Health technology assessment (Winchester, England) 2019; doi:10.3310/hta23020 PubMed 30675873
6. Honey for acute cough in children. The Cochrane database of systematic reviews 2018; doi:10.1002/ebch.1970 PubMed 29633783