Hello, my name is Dr. Kara and I have over 20 years of experience as a veterinarian. I'm sorry to hear that Delilah is so miserable with allergy symptoms this summer.
I'll give you an allergy rundown of likely causes for skin troubles. She may have more than one allergy given how symptomatic she is now. Dogs that have one allergy often develop several with time. The effect of multiple allergies aren't additive, they actually compound one another.
Even if you don't see fleas I do recommend using protection, if only during the spring
summer and early fall months. In her case this year because they are such a problem you may need to go over the winter too to catch the few eggs and larvae that are left to hatch out. They are the most common allergen and it only takes one bite a month to make an allergic dog scratch so I recommend using flea prevention even if you never see one again. Frontline Plus, Advantage II or Advantix are excellent but I have heard of some fleas becoming resistant to Frontline so perhaps a switch to Advantage products is best. Don't use over the counter products, especially Hartz or Sargents, as most are ineffective if not toxic. Flea shampoos are drying, there is no residual effect and any shampoos will wash some of your flea topical off so I don't recommend using them.
Other allergens can be inhaled (like grass pollen, dust mites or molds) and you can use a combination of antihistamines and high doses of omega-3 fatty acids to help with those (they also help with the symptoms of flea allergy). In combination fatty acids and antihistamines work synergistically, much better than either one alone. If her symptoms worsen seasonally I would think that inhaled allergens are a part of her problem.
You can try:
1)Benadryl (diphenhydramine only don't use the combination products with decongestants or acetaminophen as they can be toxic for dogs) at 1mg to 2mg per pound or one 25mg capsule per 25 pounds of dog orally every 8 hours.
OR 2)Claritin (loratidine) at 5mg per 25 pound dog once or twice daily.
OR 3)Hydroxyzine at 1mg per pound orally every 8 hours.
OR 4) Chlorpheniramine at 4mg to 8mg per dog once or twice daily.
Some dogs do better on one antihistamine rather than another.
Give the one you pick a week to 10 day trial and if it isn't working try another. Be
aware antihistamines can cause sleepiness or hyperactivity in some dogs. These
side effects do wear off with repeated use.
Omega-3 fatty acids are fish oil products. 3V by DVM or Derm Caps ES are good brand name products. Use the high end of the dosing schedule for your pup's weight.
Cool water baths with an oatmeal shampoo or chlorhexiderm shampoo (which is antibacterial and antifungal) and a conditioner with an antihistamine may help. The water rinses off allergens and the cool temperature soothes itchy skin. The white bumps that you are seeing are likely caused by a skin infection from her licking and chewing and the chlorhexidene shampoo should be helpful with that. If the infection becomes deep she will need oral antibiotics but shampooing is a good start. Skin infections make them more itchy.
Food allergy is possible with her if her itchiness seems to be all year round. Dogs can develop allergies to any protein or carbohydrate so even if she is only fed one thing that can be what she is allergic to. Dogs with food allergies tend to lick and scratch their paws, face and ears the most, but any of the "allergy reactive areas" can be affected. You could try a true hypoallergenic diet like Hills z/d or Purina Veterinary Diets HA. No treats, flavored medication or bones while on the diet and it must be used for a least 12 to 16 weeks to see the full effects. Most owners see some improvement in 8 weeks or so.
Oral cortisone can be needed in some cases to get the itch to stop and then we use antihistamines to try and stop it from coming back. These are prescriptions though and they do have side effects so we do need to be judicious with their use.
Another option if the antihistamines and omega 3's aren't enough is a product called Atopica. It suppresses the immune system a bit so it decreases allergic symptoms but it doesn't have as many harmful side effects as systemic steroids. If you are interested discuss this medication with your veterinarian as it is a prescription.
If it's been a while since her last exam parasites like cheyletiella or sarcoptes should be looked for as well if she isn't improving as both lead to very itchy skin.
Please let me know if you have any further questions.