Allergens can be inhaled, ingested or be absorbed through or have contact with the skin.Symptoms
Pruritis (itching), sweating, pilo-erection (hairs stand on end), urticaria (hives), angioderma (swollen watery plaques), hemorrhage of the skin.Treatment
First of all, try to discover the offensive agent. Review the recent history of medications, changes in feeding patterns or changes in environment. Examine the patient all over for other sites that may give clues as to the identity of the allergen. Then remove the toxin, such as weeds, drugs, etc.
Second, determine if the signs that brought the event to your attention are part of a more serious situation known as anaphylactic shock, a serious condition that can result in rapid death. Anaphylaxis is characterized by difficulty in breathing, collapse, foaming from the mouth, sunken eyes, protruding tongue, collapse, unconsciousness and eventually death. It cannot be relieved without immediate administration of heroic measures such as epinephrine (1cc per 100 lbs), which should always be kept on hand unless you can guarantee immediate access to your vet 24 hours a day, seven days a week.
Third, begin palliative treatment aimed at symptom relief. Soothing creams such as aloe vera, people hand lotion, udder balm or hydrocortisone creme can bring temporary reduction of itching. Goats have a terrible habit of vigorously chewing at areas of skin that are annoying to them, thereby making a small minor irritation into a major open wound that rapidly becomes a ready site for infection. Quick treatment of minor itching is, therefore, very important.
Over-the-counter people antihistamines are very helpful in the face of allergic reactions. These can be given at about double the label dosage.
Some skin eruptions can be the result of inhaled allergens such as can be found in feeds or environmental dust. (This is probably not so prevalent in goats as in dogs and cats, but is a topic that needs further research.)
Wherever local allergic dermatitis becomes infected, it should be treated with topical antiseptic or antibiotic preparations as appropriate. If the infection becomes severe, it might be a good idea to start penicillin shots.
Occasionally, there will be the rare doe who develops a contact dermatitis from lying on fresh alfalfa. This usually occurs around the mouth.
If any of the above situations last for more than a few days or if the symptoms become severe, you should contact your veterinarian to reconsider the diagnosis or provide medications which require a prescription.