Contact Info

Emergency contacts like your vet, a nearby animal service center, animal poison control, etc., should always be kept handy, and the first aid box is a nice place to store them carefully. Do keep these contacts saved on your mobile phone, too.
Splints

What to do if your dog suffers from a broken bone or ligament? A splint is your savior. It would minimize its movement and keep it comfortable until you get medical attention.
Gauze (Or Vet Wrap)

We all use gauze as a bandage. You can also use it as a bandage for your dog. Since it is water-resistant, it stops bleeding. You can also use it as padding for splints. Do not make bandages so tight that it suffocates them.
Antibiotic Ointment

Just like antibiotic ointment is used to clean your wounds, it would help treat and sterilize your dog’s wounds. It can help you treat minor wounds, dry skin, rashes, and even allergies. Keep in mind that you do not let your dog lick the ointment.
Muzzle

Don’t forget to put a muzzle in your dog’s kit. Even if your furry friend is the best-disciplined dog, it can become irritated and aggressive in injury or pain. So a breathable nylon muzzle is an excellent option to keep your pet from biting and be friendlier.
Conclusion
Making a separate and customized first aid kit for your pet is a sign of your compassionate care towards them. Keeping these essential items with you would help you keep them safe and prevent any infection in case of any injury or emergency. A regular veterinarian checkup is also necessary.