What are Delayed-Type Allergies

Definition of Delayed-Type Allergies

Delayed-Type Allergies (DTH) are a type of immune system reaction in which symptoms take time to appear after exposure to an allergen, typically taking hours to days to develop. Unlike immediate-type allergies, which present symptoms rapidly, DTH reactions occur gradually and can include symptoms such as skin rashes, inflammation, and even systemic symptoms such as fever and joint pain.

These reactions are mediated by T-cells, a type of white blood cell involved in the body’s immune response. Delayed-type allergies can be caused by a variety of allergens including food, medication, insect bites, and contact with certain materials and can be diagnosed through skin or blood tests. Treatment typically involves avoiding the allergen and managing symptoms through medications or immunotherapy.

Explained in plain language

Delayed-type allergies are when your body has a reaction to something, but it doesn’t happen right away. It might take a few hours or even a couple of days for the reaction to show up. It’s like playing a game of hide and seek with your body. Your body reacts to something it doesn’t like, but it doesn’t show it until later. These reactions can cause things like rashes, stomach upset, or trouble breathing.

Types of Delayed-Type Allergies

There are four common types of DTH:

1. Contact Dermatitis

This type of DTH occurs when the skin comes into contact with an allergen, such as poison ivy or certain metals, causing redness, itching, and sometimes blisters.

2. Food Allergies

Food allergies are caused by an immune system reaction to specific foods, such as peanuts or shellfish, and can cause symptoms such as hives, stomach cramps, and difficulty breathing.

3. Medication Allergies

Some people may have an allergic reaction to medications such as antibiotics, causing symptoms like itching, hives, or difficulty breathing.

4. Insect Bite Allergies

Some people may have an immune system reaction to the bites of certain insects, such as mosquitoes or bees, resulting in symptoms such as itching, redness, and swelling.

Symptoms of Delayed-Type Allergies

These symptoms may vary in severity and presentation, and that not all individuals will experience the same symptoms.  Here is a detailed explanation of the symptoms of each of the four common types of Delayed-Type Allergies (DTH):

1. Contact Dermatitis: Contact dermatitis is a type of delayed-type allergy that occurs when the skin comes into contact with an allergen, such as poison ivy, certain metals, or fragrances. The symptoms of contact dermatitis include:

• Redness: The skin may become red and irritated in the area of contact with the allergen.
• Itching: The affected skin may be itchy, causing discomfort and a urge to scratch.
• Swelling: The skin may also become swollen in the area of contact with the allergen.
• Blisters: In severe cases, blisters may form on the skin.

2. Food Allergies: Food allergies are a type of delayed-type allergy that occur when the body has an immune system reaction to a specific food, such as peanuts or shellfish. The symptoms of a food allergy include:

• Hives: Hives are raised, red, and itchy welts that may appear on the skin.
• Stomach cramps: Abdominal cramps, nausea, and vomiting may occur as a result of a food allergy.
• Diarrhea: Diarrhea may also be a symptom of a food allergy.
• Difficulty breathing: In severe cases, difficulty breathing may occur as a result of a food allergy.

3. Medication Allergies: Some people may have an allergic reaction to certain medications, such as antibiotics, causing a delayed-type allergy. The symptoms of a medication allergy include:

• Itching: The skin may become itchy in response to a medication allergy.
• Hives: Hives may appear on the skin as a result of a medication allergy.
• Rash: A rash may form on the skin as a result of a medication allergy.
• Difficulty breathing: In severe cases, difficulty breathing may occur as a result of a medication allergy.

4. Insect Bite Allergies: Some people may have an immune system reaction to the bites of certain insects, such as mosquitoes or bees, resulting in a delayed-type allergy. The symptoms of an insect bite allergy include:

• Itching: The skin may become itchy in response to an insect bite.
• Redness: The skin may become red in the area of the insect bite.
• Swelling: The skin may become swollen in the area of the insect bite.
• Warmth: The skin may feel warm in the area of the insect bite.

Causes of Delayed-Type Allergies

The causes of Delayed-Type Allergies (DTH) can vary depending on the type of allergy, but in general, they result from a complex interaction between the immune system and an allergen. Here is a more detailed explanation of the causes of each of the four common types of DTH:

Contact Dermatitis

Contact dermatitis is caused by contact with an allergen, such as poison ivy, certain metals, or fragrances. When the skin comes into contact with the allergen, the immune system responds by producing an allergic reaction, resulting in inflammation and the symptoms of contact dermatitis.

Food Allergies

Food allergies are caused by the immune system reacting to a specific food, such as peanuts or shellfish. When a person with a food allergy eats the allergenic food, the immune system produces antibodies that attack the food, leading to an allergic reaction and the symptoms of a food allergy.

Medication Allergies

Medication allergies can occur when the immune system reacts to a specific medication, such as antibiotics. The immune system produces antibodies that attack the medication, leading to an allergic reaction and the symptoms of a medication allergy.

Insect Bite Allergies

Insect bite allergies are caused by the immune system reacting to the bites of certain insects, such as mosquitoes or bees. When a person is bitten by an insect, the immune system produces antibodies that attack the insect’s venom, leading to an allergic reaction and the symptoms of an insect bite allergy.

Not everyone who comes into contact with an allergen will experience an allergic reaction. Individual factors, such as genetics, can influence the development of DTH. Additionally, some people may have multiple allergies or experience more than one type of DTH.

Diagnosis of Delayed-Type Allergies

Diagnosing DTH can be a complex process and may involve a combination of different diagnostic tools. Here are some common methods used to diagnose DTH.

Skin Testing

Skin testing is a common method used to diagnose DTH, particularly for contact dermatitis and insect bite allergies. During skin testing, a small amount of the allergen is placed on the skin, and the skin is then scratched or pricked. If a person is allergic to the allergen, they will experience a red, raised, itchy bump at the site of the allergen.

Blood Testing

Blood testing, such as the RAST (RadioAllergoSorbent Test), can be used to diagnose food allergies, medication allergies, and other types of DTH. During blood testing, a sample of blood is taken and sent to a laboratory for analysis. The laboratory will look for antibodies to specific allergens, which indicate an allergy.

Patch Testing

Patch testing is a type of skin testing used to diagnose contact dermatitis. During patch testing, small amounts of the allergen are placed on patches, which are then applied to the skin. The patches are left in place for 48 hours and then removed. If a person is allergic to the allergen, they will experience a red, raised, itchy bump at the site of the allergen.

Oral Food Challenge

An oral food challenge is a diagnostic tool used to diagnose food allergies. During an oral food challenge, the person is given small amounts of the suspected allergenic food to eat, gradually increasing the amount until a full serving is consumed. If a person is allergic to the food, they will experience symptoms such as itching, hives, or abdominal pain.

Elimination Diet

An elimination diet can be used to diagnose food allergies. During an elimination diet, the person eliminates all suspected allergenic foods from their diet for several weeks. If the person experiences improvement in their symptoms, the suspected allergenic foods are then added back into the diet one at a time to see if symptoms return.

Treatment of Delayed-Type Allergies

The treatment depends on the type of allergy and the severity of symptoms. Here are some common treatments for DTH:

• Avoidance: Avoiding exposure to the allergen is the most effective way to prevent symptoms of DTH. This may involve removing the allergen from the environment, switching to a different product, or avoiding certain foods.
• Medications: Over-the-counter antihistamines, such as diphenhydramine (Benadryl) or cetirizine (Zyrtec), can be used to relieve itching and swelling. Corticosteroid creams or ointments can also be used to relieve itching and swelling. For severe symptoms, prescription-strength corticosteroids may be required.
• Desensitization: Allergen immunotherapy, also known as desensitization, can be used to treat certain types of DTH, such as insect sting allergies. During allergen immunotherapy, the person is given increasing doses of the allergen over a period of time, which helps to reduce the severity of symptoms if the allergen is encountered in the future.
• Antibiotics: If a skin infection is present, antibiotics may be prescribed.
• Pain Medications: Over-the-counter pain relievers, such as ibuprofen, can be used to relieve pain.

Prevention of Delayed-Type Allergies

Prevention involves avoiding exposure to the allergen that triggers the allergy. Here are some ways to prevent DTH:

• Identify the allergen: A healthcare professional can help you determine what is causing your allergy and help you avoid exposure to that allergen.
• Avoid certain foods: If you have a food allergy, avoid eating the food that triggers your allergy.
• Avoid certain products: If you have a cosmetic or skin product allergy, switch to products that do not contain the allergen.
• Avoid insect stings: If you are allergic to insect stings, avoid being outside during times when insects are active and take measures to protect yourself, such as wearing protective clothing and using insect repellent.
• Get vaccinated: If you are allergic to insect stings, consider getting a vaccine that can help reduce the severity of symptoms if you are stung.
• Allergen immunotherapy: Allergen immunotherapy, also known as desensitization, can be used to prevent symptoms of DTH in some cases. During allergen immunotherapy, the person is given increasing doses of the allergen over a period of time, which helps to reduce the severity of symptoms if the allergen is encountered in the future.

In conclusion, Delayed-Type Allergies (DTH) are a type of allergy that occurs when the immune system reacts to an allergen several hours after exposure. DTH can cause a range of symptoms, including itching, redness, and swelling, and can be triggered by a variety of allergens, including foods, cosmetics, insect stings, and medications.

It is recommended to seek medical attention if you experience symptoms of DTH. A healthcare professional can help you determine the cause of your allergy and develop a treatment plan that is right for you. With proper treatment and prevention, it is possible to manage symptoms of DTH and live a comfortable, active life.

Dr Martha Howard