Antibiotics for Chicken Respiratory Infection: What Actually Works

Respiratory illness is one of the most misunderstood problems in a backyard flock, and the misunderstanding costs birds. The instinct is to grab whatever antibiotic is on the shelf — usually amoxicillin or a fish antibiotic — and hope. This guide explains what you're actually dealing with, which drugs work and which are a waste of time, and the honest limits of treatment, all grounded in veterinary references rather than the guesswork that fills most forum threads.

How to recognize a respiratory infection

The signs are usually easy to spot once you know them. You'll see some combination of:

• Rattling, gurgling, or raspy breathing — often the first thing you hear at night on the roost.
• Sneezing and nasal discharge.
• Watery, bubbly, or foamy eyes, sometimes with swelling around the eye.
• Swollen face or sinuses (infectious sinusitis is another name for the same disease).⁴
• Coughing, head-shaking, and reduced appetite or laying.
• Open-mouth breathing or gasping — a sign of a serious, advanced case that needs urgent care.

Why the antibiotic choice matters so much

Here's the single most useful thing on this page. The most common cause of chronic respiratory disease in chickens is Mycoplasma gallisepticum, and Mycoplasma is a strange bacterium: it has no cell wall. Penicillin-class antibiotics — amoxicillin, ampicillin, penicillin itself — work by attacking the bacterial cell wall. With no wall to attack, they simply don't work against Mycoplasma.¹ This is why so many keepers dose with leftover amoxicillin and see nothing improve.

The antibiotics veterinary references cite as effective against Mycoplasma are:

On tylosin dosing — a sourced range, not a prescription

Because keepers ask for numbers, here is what the peer-reviewed work shows, presented as reference: in controlled trials, tylosin at about 35 mg/kg body weight daily for 5 days in drinking water significantly reduced respiratory signs and lesions — and notably, a higher 100 mg/kg dose was not more effective than 35 mg/kg.³ A separate pharmacokinetic study landed on a similar figure (about 45 mg/kg daily for 3 days).⁶ Treat those as the published range. The exact product, concentration, and legality for laying hens vary a great deal, so confirm with a vet before dosing — this is reference information, not a personal prescription.

What to do right now, step by step

Step 1 — Isolate the sick bird

Move it away from the flock immediately into a warm, dry, well-ventilated spot. Mycoplasma spreads through respiratory droplets and direct contact, so every hour a sick bird stays with the flock raises the odds the whole coop goes down.¹

Step 2 — Support breathing and strength

Keep the bird warm and, crucially, keep it eating and drinking. Add vitamins and electrolytes to the water. Cut dust and ammonia in the coop — both irritate an already-inflamed airway and feed secondary infection. Good air quality is genuinely part of the treatment.

Step 3 — Confirm the cause, then treat

Several diseases (infectious bronchitis, infectious coryza, ILT, aspergillosis) can mimic Mycoplasma, and the right treatment differs. A vet can confirm with a swab or PCR test.⁵ That matters because if it's viral (like infectious bronchitis), antibiotics won't touch the virus — they'd only be for preventing secondary bacterial infection. Match the drug to the actual diagnosis.

Step 4 — Decide on your flock's future

This is the hard part nobody mentions. Because antibiotics suppress but never eliminate Mycoplasma, a recovered bird is a lifelong carrier that can relapse under stress and infect any new birds you add.¹ Many keepers respond by running a closed flock (no new birds in, no birds out) after an outbreak. It's a real decision worth making deliberately, not by accident.

Prevention

• Buy from Mycoplasma-free (NPIP-clean) sources — the single most effective prevention is not bringing it home in the first place.¹
• Quarantine every new bird for 2–4 weeks before it meets the flock.
• Keep the coop dry, ventilated, and low in dust and ammonia — poor air quality is a direct trigger.
• Reduce stress (overcrowding, extreme cold, predator pressure), which brings on relapses in carriers.

Frequently asked questions

What antibiotic is best for a chicken respiratory infection?

For Mycoplasma, the usual cause, macrolides like tylosin and the tetracyclines are the drugs veterinary references cite, because Mycoplasma is susceptible to them. Amoxicillin does not work. The specific drug and dose — and whether antibiotics are even the right answer — should be confirmed with a vet based on the actual pathogen.

Why doesn't amoxicillin work?

Mycoplasma has no cell wall, and penicillins like amoxicillin work by attacking the cell wall. With nothing to attack, they're ineffective, which is why leftover amoxicillin usually does nothing here.

Can a chicken recover from a respiratory infection?

Yes, birds usually improve with the right antibiotic and supportive care, but the infection isn't eliminated — a recovered bird stays a lifelong carrier that can relapse and infect others, which is why many keepers keep a closed flock afterward.

How do I know if my chicken has a respiratory infection?

Rattling or gurgling breathing, sneezing, nasal discharge, watery or bubbly eyes, and facial swelling are the classic signs. Because several diseases share them, a vet swab or PCR gives the definitive answer.

Is it contagious to other chickens?

Very. It spreads through respiratory droplets and direct contact and can pass through eggs to chicks. Isolate a sick bird immediately.

Can I catch it from my chicken?

Mycoplasma gallisepticum is a poultry pathogen and not a meaningful risk to most people, but wash your hands after handling sick birds and see a doctor if you develop symptoms.

Can I eat the eggs?

The infection itself isn't an egg food-safety issue, but if you treat with antibiotics, follow the label's egg withdrawal period exactly and discard eggs during it. Many of these drugs also require veterinary oversight in layers.

Will it kill my chicken?

Mycoplasma alone usually causes high illness but low death rates. The real danger is secondary infection piling on top, which is why prompt treatment and clean coop air matter.

How we reviewed this article

This guide draws on the Merck Veterinary Manual, poultryDVM, university extension resources, and peer-reviewed efficacy studies rather than forum guesswork. Every clinical claim is numbered to a source below. Antibiotic dosing is presented as a sourced research range with explicit legality and egg-withdrawal cautions, never as a personal prescription — the correct drug and dose for a specific bird is a veterinary decision. This page is scheduled for review by a licensed veterinarian; the reviewer's name and date will appear here once complete.

Sources & references

1. Merck Veterinary Manual. Mycoplasma gallisepticum Infection in Poultry. Susceptibility to tylosin/tetracyclines, resistance to cell-wall drugs, no elimination of infection, prevention. merckvetmanual.com
2. poultryDVM. Mycoplasma gallisepticum. Diagnosis (rtPCR, HI), clinical picture. poultrydvm.com
3. Garmyn A, et al. Efficacy of Tylosin and Tilmicosin Against Experimental M. gallisepticum Infection in Chickens. Avian Diseases, 2019. Tylosin 35 mg/kg/day x5 effective; 100 mg/kg not more so. pubmed.ncbi.nlm.nih.gov
4. extension.org (Poultry). Mycoplasmas in Poultry. CRD / infectious sinusitis synonyms and species affected. poultry.extension.org
5. poultryDVM / The Poultry Site. Antibiotic classes active against Mycoplasma (macrolides, tetracyclines, fluoroquinolones, lincosamides, pleuromutilins) and diagnostic testing. thepoultrysite.com
6. Zhang N, et al. Prudent Use of Tylosin for Treatment of M. gallisepticum Based on Clinical Breakpoint. PK-PD regimen ~45.88 mg/kg daily x3. ncbi.nlm.nih.gov

Sources current as of September 2026. Educational content, not a substitute for veterinary care. Antibiotic use in poultry is regulated; consult a veterinarian.