Hello and welcome
The pyracantha or firethorn berries are considered toxic, the berries are the most toxic part, and could cause vomiting, stomach ache, blistering of tongue, and diarrhea if ingested. In small amounts only mild symptoms may be seen. All members of this plant produce hydrogen cyanide which is at the highest levels in the berries and leaves. While the levels are low if a large amount of the berries are consumed at once it could be fatal.
While I can find no information on long term effects of ingesting these berries because they do produce cyanide I would worry that constant ingestion could cause toxic build up in the blood.
Here is more on this plant
I hope this has been helpful, please reply back if you have additional questions or concerns.
Our 65 lb. lab. 12 years old..had a seizure of some type last evening. She is fine now.
Local vets have suggested mushrooms or pyracantha as the cause....can you con firm this?
None of my information states that the pyracantha can or does cause seizures only digestive problems such as stated in my above answer. Certain mushrooms can cause seizures even if ingested in small amounts.
Should this happen again I would be more suspicious of a health condition.
Labs are known to develop seizures due to epilepsy