What rosemary does to dogs and the effects it can have on them:

Rosemary is an aromatic herb that is popularly used for cooking and in natural medicine. However, rosemary essential oil and the herb itself can be toxic to dogs if ingested or applied topically in high amounts. Understanding the effects of rosemary on canines can help dog owners use this herb safely around their pets.

Ingestion of Rosemary

The leaves and oil extracted from the rosemary plant contain several potentially harmful compounds that can affect dogs if consumed orally. The main compounds include camphor, 1,8-cineole, borneol, bornyl acetate, and other terpenes.

In small amounts, ingestion of rosemary may simply cause mild stomach upset or irritation. However, in larger doses it can result in more serious side effects:

• Vomiting, diarrhea

• Abdominal pain

• Neurological signs like tremors, seizures or twitching

• Depression, lethargy

• Increased body temperature

• Increased heart rate and blood pressure

• Respiratory distress
  

A 2013 case report described two dogs who developed seizures after ingesting homemade food seasoned with rosemary. One dog experienced cluster seizures while the other had a single seizure (1).

This demonstrates the neurotoxic effects rosemary can have. Camphor toxicosis is known to cause central nervous system depression and seizures in dogs. Even small ingestions warrant veterinary monitoring due to the risk of delayed seizures (2).

Topical Application of Rosemary

While the toxicity of ingested rosemary is better documented, topically applied rosemary can also pose risks:

• Skin irritation or allergic dermatitis. Rosemary contains multiple compounds that may irritate the skin. Essential oils in particular can cause reactions when applied undiluted. Patch testing is advised before any full body or leave-in treatments (3).

• Misuse of essential oils. Highly concentrated essential oils should be diluted before topical use. Improper or excessive use increases the risk of toxicity as the oil gets absorbed into the body (4).

• Eye injury. Getting pure rosemary oil or extracts in the eyes can damage the cornea and cause vision impairment or blindness. Extreme care is needed when using around a dog's face.

• Ingestion through licking. Dogs may lick off any rosemary oil, extracts or rinses applied topically. This can lead to oral toxicity if a large amount is ingested. Monitoring is necessary to prevent licking.
  

Potential Benefits of Rosemary for Dogs

While rosemary does carry risks if misused, it also has some potential therapeutic benefits that may make topical use appealing for dogs when done safely:

• Antimicrobial effects may help treat skin infections when applied in very dilute concentrations (5).

• Anti-inflammatory effects that can soothe skin irritation, rashes or bug bites when used in proper dilutions (6).

• Improved circulation when used sparingly in shampoos or sprays may help stimulate hair growth and skin health (7).
  

However, there is still minimal scientific research on rosemary's effects in dogs specifically. Evidence for benefit is limited and using rosemary does come with hazards. Consulting a veterinarian before use is best.

Safe Use of Rosemary Around Dogs

While internal administration of rosemary should be avoided, cautious external use may be permissible if done carefully:

• Always dilute essential oil in a carrier oil before applying to a dog topically. Recommended dilution is 0.5-1% for most essential oils (8).

• Do not let dogs ingest rosemary essential oil, extracts, or rinses even in small amounts. Seek emergency vet care if ingestion is suspected.

• Monitor for skin irritation during a patch test. Discontinue use if any negative reactions occur.

• Avoid contact with eyes, nose and mucus membranes. Use sparingly around the face.

• Do not use rosemary essential oil or extracts undiluted. Also avoid use on dogs with epilepsy or seizures due to neurotoxic risks.

• Discuss any intended use of rosemary for your dog with your veterinarian first to determine if it may be helpful or harmful for your pet's unique needs.
  

References:

1. https://onlinelibrary.wiley.com/doi/full/10.1111/jvp.12173

2. https://pubmed.ncbi.nlm.nih.gov/9918288/

3. https://www.sciencedirect.com/science/article/pii/S1090023315000223

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073409/

5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6165352/

6. https://www.sciencedirect.com/science/article/abs/pii/S175646462100161X

7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4289931/

8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073409/