Is sunscreen harmful for our pets?
Safety of sunscreen
There is considerable debate surrounding the safety of sunscreen. From a human point of view there is concern that many of the chemicals within sunscreen actually cause more harm than good. It has been suggested that they or the products into which they break down following sun exposure can be absorbed by the skin and possibly deeper tissues and organs where they can cause harm. In humans it has been suggested that these chemicals or their breakdown products may even contribute to skin cancer and organ damage. Sunscreen safety is an area where opinions are as divided as they are strongly held and in such situations the truth is usually somewhere in the middle ground.
Generally speaking chemicals are absorbed through the skin in low levels and because our pets have shorter lives than us, the chances of chemicals affecting pets through this route are unlikely. Absorption of chemicals through the skin over the lifetime of a human may be of more concern and for more information about the possible harmful effects of sunscreen chemicals please go to http://breakingnews.ewg.org/2011sunscreen/
Ingestion of sunscreen
For pets it is ingestion of sunscreen that presents more of a threat than skin absorption. This doesn’t just mean you have to be vigilant of your dog chewing a sunscreen bottle and eating its contents, but you also have to be aware of the dangers of them licking sunscreen from your skin or their own if you have applied it to them.
Some pets are more susceptible to sun burn than others. When a dog or a cat has a white coat or patches of white, the skin under the fur is usually white too. If the fur is short or sparse then this skin can be burnt by the sun. The coat is often sparse on the bridge of the nose, the underbelly, groin and arm pits of dogs. Cats often have sparse hair cover between the eye and the ear and on the ear flaps themselves. Pink skin found on the nose and eyelids of dogs and cats is also susceptible to sunburn.
While sunscreen should not be applied to the eyelids or the nose, it can be applied to the other vulnerable areas on a pet. Both dogs and cats are very adept at licking off sunscreen so care needs to be taken to ensure that the product you have used is not toxic if ingested. Only use a sunscreen on your pet that is labeled as safe for pets. Some vets say that using baby sunscreen may also be safe because children are at similar risk of poisoning by ingestion as pets. However, I would not recommend this, especially for cats, which are more susceptible to poisoning than both dogs and babies.
Ingredients of which to be aware
One of the more dangerous components of sunscreen is PABA (para-aminobenzoic acid). Ingestion of PABA can cause vomiting, diarrhoea, bone marrow changes and liver damage. PABA sunscreens also contain 50 percent or more ethanol alcohol so ethanol toxicity is a greater risk in the short term. However, most modern sunscreens are now PABA-free because it commonly causes allergic reactions in humans. Thus the risk of PABA is generally no longer a cause for concern. The chemicals in current human sunscreen that are poisonous when ingested by dogs and cats are:
- Cinnamates cinoxate, ethylhexyl, Octyl & p-methoxycinnamate
- PABA esters Padimate-O, Octyl Dimethyl PABA
- Salicylates ethylhexyl salicylate, homosalate, octyl salicylate
- Propylene Glycol as a humectant in sunscreens to extend activity time
- Zinc oxide physically blocks UVA and UVB
Symptoms of poisoning following ingestion
When small amounts of human sunscreens are ingested by dogs or cats the most likely symptom is self-limiting vomiting,and diarrhoea due to stomach irritation and nausea. However if large quantities of sunscreen are ingested the symptoms will vary depending upon the component chemicals in the product.
Cinnamates and PABA esters are chemical groups that block UVB radiation. They may be used alone, together, or with other chemicals. They are mildly toxic if ingested and cause stomach irritation.
Salicylates protect against a small part of the UVB spectrum and must be used in high concentrations. They are are aspirin-like substances and, if ingested in large quantities, can cause aspirin poisoning in dogs. Cats are particularly sensitive to aspirin and ingestion of even small quantities can cause poisoning. For this reason cat owners must take care that their pets are not exposed to sunscreen containing salicylates.
Propylene Glycol is a component of some sunscreens and extends their protective properties and helps maintain the skin’s hydration. Propylene Glycol is also a component of ‘safer’ anti-freeze (compared to ethylene glycol which is more toxic). If ingested by dogs and cats, propylene glycol initially causes symptoms like drunkenness because it affects the nervous system. If left untreated, it can result in liver and kidney dysfunction. It is likely that cats are more susceptible to poisoning with propylene glycol than dogs.
Zinc oxide is used as a physical block to harmful UVA and UVB radiation. Zinc is a mineral that is essential for health but if ingested in excess it can cause poisoning. Unattended dogs will occasionally ingest large amounts of zinc oxide in human sunscreens or ointments.
Zinc toxicity in dogs may have numerous symptoms:
- Excessive and continuous vomiting and diarrhoea
- Lack of appetite, lethargy and weakness.
- Liver failure and jaundice
- Kidney failure and red urination
- Anaemia, pale gums
Pets are less likely to be at risk of long-term skin absorption issues related to sunscreens compared to humans, but pets are more at risk of ingesting sunscreens and subsequent poisoning.
It is safest to use sunscreens developed for animals on your pets. Cats are particularly at risk from some of the chemical components of human sunscreens and even some sunscreens that are considered safe for dogs and horses may not be safe for cats!
Surprisingly many sunscreens licensed for pets contain chemicals that could cause problems such as Octyl Dimethyl PABA, Octyl methoxycinnamate, Propylene Glycol and Zinc Oxide.
To protect white areas of cat’s ear flaps, it is best to use products containing Titanium Dioxide as their active ingredient. Titanium Dioxide works by physically blocking the sun's harmful UVB rays and short UVA rays, but does not block the longer UVA rays. So while Titanium Dioxide is not poisonous, it does not completely protect against the sun’s rays and is often combined with other ingredients such as zinc oxide to increase protection.
It appears that the perfectly safe sunscreen for pets does not yet exist!
David Chamberlain BVetMed., MRCVS.
Veterinary Consultant to PetSafe®