The delayed-reaction allergies only arise after several hours or days. It is generally caused by the interaction between the allergen and T cells which is another form of white blood cell. Various substances can trigger delayed-reaction allergies.
What are the contact reactions?
Poison ivy and other similar plants trigger some of the well-known delayed-reaction allergies. Upon initial exposure to the plant, there is no reaction for the first 24-48 hours. Once the itchiness, rash and blisters arise, an allergic reaction to poison ivy might take 8 weeks to settle.
Other usual sources of delayed-reaction allergies include metals such as cobalt and nickel, formaldehyde, antibiotic present in several topical ointments and potassium dichromate which is a tanning agent present in clothing and leather shoes.
Additionally, latex allergy which is becoming common among healthcare professionals can lead to delayed-reaction allergies.
The drug reactions can arise right away or as a delayed hypersensitivity reaction. Penicillin and other similar antibiotics are the usual cause of a reaction and can arise as a delayed reaction.
Some of the allergic reactions can cause serum sickness which includes weakness, fever, joint pain, hives and swollen lymph nodes. Even though antibiotics are typically linked with delayed-reaction allergies, any medication including anesthetics, anticonvulsants, heart medications and even preservatives can be culprits.
What are the food reactions?
The food reactions are the usual causes of a delayed-reaction allergy that arise 8 hours or more after ingestion. The common highly allergenic foods include mollusks, legumes, fish, eggs, wheat, crustaceans and tree nuts.
Even food additives such as monosodium glutamate, sulfites and aspartame can also trigger a delayed-reaction allergy.