Every spring, as California’s green hills bleach to gold, foxtail season begins. If you hike with your dog — or even walk near dry grassland — foxtails are the hazard most vets wish more owners understood before they become a problem.

Unlike thorns, foxtails don’t just poke and fall out. Their barbed structure is designed by evolution to move in one direction only: forward. Once one enters skin, an ear canal, a nostril, or the space between toes, it burrows deeper with each movement of your dog’s body. Left undetected, a foxtail can migrate through tissue and reach internal organs.

What foxtails are

Foxtails are seed heads from wild barley (Hordeum murinum) and similar grasses common throughout California. In spring they’re green and flexible. By May or June, they dry out, detach, and begin hitchhiking on anything that brushes past — including fur, socks, and shoelaces.

Peak season runs roughly May through October, though in coastal and inland areas with mild winters, dry grasses can persist nearly year-round. They grow from Central Valley grasslands to Bay Area fire roads, Marin County trails, foothill parks, and the dry buffer zones around suburban walking paths.

How they embed — and why they don’t come back out

The seed head’s surface is covered in backward-pointing barbs. When a foxtail contacts fur, it orients itself tip-first and advances with any motion that compresses or moves the fur around it. Dogs accelerate the process by scratching, shaking, or licking the site.

Once embedded, foxtails rarely come out on their own. They don’t dissolve. They don’t show up reliably on X-ray, though some vets use ultrasound to locate them. A foxtail that enters the nasal passage can reach the brain. One that penetrates the chest wall can cause pneumothorax. The longer a foxtail stays in, the more serious — and expensive — the treatment.

Where to check your dog after every outing

Run your hands through your dog’s coat immediately after trail time. Pay particular attention to:

• Between the toes and under paw pads — the most common entry point
• Ear canals — a foxtail in the ear causes sudden, violent head shaking and pawing at the ear; this is a same-day vet visit
• Nostrils — repeated violent sneezing that starts mid-hike is the signature symptom
• Armpits and groin — thin-furred areas where foxtails embed easily and are easy to miss
• Under the collar — a spot owners routinely overlook
• Eyes — squinting, tearing, or pawing at an eye warrants same-day attention regardless of cause

Dogs with longer, thicker coats — golden retrievers, spaniels, setters, standard poodles — are at higher risk because foxtails tangle in fur before they can brush off.

Symptoms that mean call the vet today

Don’t wait to see if things resolve on their own. See a vet the same day if your dog shows:

• Sudden onset of violent sneezing that won’t stop
• Head tilting or intense ear scratching after a hike
• Limping combined with a swollen paw that appeared within hours of trail time
• Eye discharge or squinting that started on or after a trail outing
• A lump under the skin appearing within days of a hike, especially if it’s draining

Foxtails removed early — when the vet can locate and extract them cleanly — are a quick outpatient procedure. Foxtails that have migrated deep into tissue may require general anesthesia, imaging, and surgery. Early extraction costs tens of dollars. Late extraction can cost thousands.

Practical prevention

You can reduce but not eliminate risk. The most effective habits:

• Full coat check within 10 minutes of leaving the trailhead — the sooner you find one, the shallower it is
• Stay on established trail surfaces and avoid scrambles through dry grass, especially at trail edges
• Trim fur around paws and ears before summer hiking season, particularly for long-coated breeds
• Consider mesh trail boots for dogs with recurring paw foxtail issues — several brands make lightweight versions that stay on during hikes
• Avoid peak-risk trails with tall dried grass from late May through the first fall rains, or shorten the outing and stick to paved paths

California hikers often treat foxtails as a minor annoyance. Veterinarians see them differently. Foxtails cause serious, sometimes life-threatening injuries every summer, and most were preventable with a two-minute post-hike check at the trailhead before loading up the car.