# Seasonal health risks for dogs > Live situation record from CLSTR: https://clstr.news/situations/seasonal-health-risks-for-dogs > Updated: 2026-09-27T06:00:13.000Z. Sources: 16. Developments: 7. Veterinary experts and health guidance have highlighted various seasonal risks for dogs during the transition into autumn. Initial guidance focused on physical activity and nutrition, advising owners to increase exercise duration gradually to prevent injuries. Dietary warnings were issued regarding high-calorie treats, while environmental hazards such as grass seeds and wild mushrooms were identified as significant dangers. Recent warnings have expanded to include specific botanical toxins. Horse chestnuts have been identified as a major risk; they contain aesculin, which is toxic in the leaves, flowers, bark, and seeds. Beyond chemical poisoning, consuming chestnuts can cause physical intestinal obstructions. Symptoms like vomiting and diarrhea typically appear within two days, with puppies being particularly vulnerable to curiosity-driven ingestion. In Slovenia and Croatia, veterinarians have issued urgent warnings regarding Colchicum autumnale, also known as autumn crocus or autumn meadow saffron. All parts of this plant—including flowers, leaves, seeds, and bulbs—contain colchicine, a potent alkaloid that inhibits cell division. Ingestion can cause excessive salivation, bloody vomiting, abdominal pain, and difficulty breathing. Severe cases may lead to organ failure in the liver and kidneys, shock, or death. Experts advise seeking immediate veterinary attention even if symptoms are not yet present, and suggest providing a plant sample or photograph to assist in diagnosis. In the United Kingdom, the PDSA has expanded the list of seasonal hazards for dogs and cats. Beyond the autumn crocus, they warn that grapes and grape-containing products are toxic. Acorns from oak trees may also cause stomach upset or intestinal blockages. Additionally, common garden plants such as azaleas, rhododendrons, chrysanthemums, ivy, holly, mistletoe, and hydrangea can be harmful, as can onions and garlic. Owners are cautioned that symptoms of ingestion may include vomiting, diarrhea, low energy, loss of appetite, pale gums, drooling, tremors, or difficulty breathing. ## Timeline ### 2026-09-27: Autumn plants and seeds pose toxicity risks to pets The PDSA warns pet owners that common autumn finds like autumn crocus, acorns, conkers, and certain garden plants can be toxic or cause blockages in dogs and cats. 4 sources. https://clstr.news/cluster/autumn-plants-and-seeds-pose-toxicity-risks-to-pets ### 2026-09-23: Autumn crocus poses fatal toxicity risk to dogs Pet owners are warned that the autumn crocus (Colchicum autumnale) is highly toxic to dogs. Ingesting any part of the plant can cause severe poisoning, organ failure, and death. 3 sources. https://clstr.news/cluster/autumn-crocus-poses-fatal-toxicity-risk-to-dogs ### 2026-09-22: Autumn hazards pose poisoning risks to dogs Veterinarians warn that autumn items like horse chestnuts, mushrooms, and acorns can be toxic or life-threatening to dogs. 3 sources. https://clstr.news/cluster/autumn-hazards-pose-poisoning-risks-to-dogs ### 2026-09-18: Mushroom foraging season brings culinary tips and pet safety warnings Autumn mushroom foraging brings culinary opportunities and safety risks, including advice on sautéing techniques and warnings regarding toxic mushroom ingestion in domestic dogs. 2 sources. https://clstr.news/cluster/mushroom-foraging-season-brings-culinary-tips-and-pet-safety-warnings ### 2026-09-12: Autumn hazards pose risks to dogs Dog owners are warned to watch for autumn hazards like wild mushrooms, acorns, and chestnuts, which can cause poisoning or organ damage in pets. 2 sources. https://clstr.news/cluster/autumn-hazards-pose-risks-to-dogs ### 2026-09-09: Veterinary experts warn of seasonal health risks for dogs Veterinarians warn dog owners of seasonal risks, including painful grass seed penetrations and poisoning from wild mushrooms, chestnuts, or fallen fruit during autumn walks. 2 sources. https://clstr.news/cluster/veterinary-experts-warn-of-seasonal-health-risks-for-dogs ### 2026-09-04: Dog health guidance for autumn exercise and dietary safety Guidance for dog owners highlights the need for gradual exercise increases during autumn to prevent injury and warns against feeding speculoos biscuits due to risks of obesity, kidney issues, and toxicity. 2 sources. https://clstr.news/cluster/dog-health-guidance-for-autumn-exercise-and-dietary-safety --- Cite as: Seasonal health risks for dogs. CLSTR, https://clstr.news/situations/seasonal-health-risks-for-dogs