Why Does My Dog Scratch All The Time?

Roundworms should not cause itching.  They are transmitted through a fecal-oral route.  Dogs often get it from ingesting infected soil.  Some pet stores may carry de-worming medication but I would recommend getting appropriate treatment from your veterinarian. 
There are many causes of itching in dogs.  Common causes include allergies and dermal parasites--like mites and ringworm.  Talk to your veterinarian about having skin tests done to check for mites and ringworm.  Allergies are about control not cure.  You and your veterinarian will work together to come up with a multi-modal treatment plan.

AnnaFalkDVM has good advice. I would also give the dog a distilled vinegar water bath because it is soothing to the skin and isn't harsh like soaps.

A dog can scratch itself due to many reasons like to mention a few liver disease, lice, fungus, fleas or anxiety. However the most common cause is allergies and it tends to get worse as the dog gets older. Among mammals, dogs and cats are the pets most frequently seen with allergies. To relieve the itching sensation, dogs may scratch and bite themselves or rub their face with their paws and other objects.

Unfortunately there is no permanent remedy for the condition and in the words of a veterinarian "are a lifelong problem", however there are some treatments to relieve the itch and cure infections and scars as a result of constant scratching, and even "desensitize" a pet to substances that cause allergies.

The reasons for allergies could be numerous like they could be due to fleas, the food they eat, airborne particles in the air they breathe in, or allergies due to physically touching something. We should find the key to the dog's itchiness and make it comfortable. Determining the reason of allergies will give us a key to solve the problem.

They may scratch because they have some sort of dry skin condition. You could try to get a shampoo that is moister rich and conditioner too. Also when you bathe the dog try to make sure all the soap is off there fur and skin before you dry them this may cause skin irritation as well good luck.

It doesn't have to be fleas for your dog to be scratching. She has dry skin. Use a shampoo, those are not expensive. You can find those at the pet shop. Something similar to this, use it as a guide: itchy skin shampoo

Thanks 2 everyone!

He may have ticks or fleas, check him for this and get him a collar if it isn't he may have some type of rash, get him checked out at the vet

If your dog doesn't have flees, I would check into a food supplement from Dinovite. My friend uses a supplement from Dinovite for her boxer and she rarely scratches now.

My poppy keep scratching  n biting , should I give her a piriton tablet ?  Now
' but later we will be getting  her some  flea treatment just in case its fleas. Poppy is I year old now  !