Summarize this article in one sentence.
While Benadryl is generally safe for dogs, every dog is different. It's best to talk to your vet before giving your dog Benadryl, to make sure it will be safe and to get a dose recommendation.  Technically, Benadryl hasn't been approved by the FDA for cats and dogs, but most vets agree it's safe. Discussing dosage with your vet is important because dogs can overdose on Benadryl. One use for Benadryl is treating anxiety in dogs. For instance, some dogs have storm anxiety, and Benadryl can help calm them down. Often, it works best to give them Benadryl ahead of the storm. Similarly, it can also help out in the car. It can calm anxiety, and it will also assist with nausea from motion sickness. Another common use for Benadryl is to treat allergies. Dogs with allergies tend to scratch more, and if your dog has been diagnosed with allergies, Benadryl can help alleviate the symptoms. However, some experts question the effectiveness of Benadryl for general allergies. While it can be helpful for reactions like bee stings and hives, it may not help as much with the itchy skin that comes with canine allergies. One of Benadryl's side effects is drowsiness. In fact, it's used in many over-the-counter sleep aids. That's why it can help your dog with insomnia if you give it to the dog before bedtime. In the United States, most products with the Benadryl label only contain diphenhydramine. However, this ingredient has fallen out of use in other countries. For instance, in the UK, cetrizine is the active ingredient instead. While this ingredient is also dog-safe, it won't have all the same effects.

Summary:
Discuss it with your vet. Treat anxiety with Benadryl. Use Benadryl for allergies and bug bites. Give Benadryl to your dog for insomnia. Ensure your product only contains diphenhydramine.