Introduction

Imagine, stepping outside on a warm late summer’s day, ready to breathe in the fresh air and enjoy the day, but instead you start to experience a runny nose, a cough, and continuous sneezing. Well, this describes the familiar symptoms associated with Ragweed allergies.¹

Ragweed pollen is an allergen that creates an adverse immune reaction in many individuals from mid-August to late September. However, due to the current effects of global warming, the allergen-producing Ragweed plants may still produce their pollen as long as October. As mentioned, it is a common allergy that affects 10-20% of the population in the United States of America and in Europe, the pollen sensitization rate is 14%.^2,3

What is ragweed?

Ragweed is a type of weed that is primarily found in suburban and rural areas of North and Central America but also exists in many other areas worldwide.¹ It is often referred to as an annual plant, as it only lives one season, but within this season it is capable of creating millions of pollen grains, which can be distributed across long distances. The Ragweed has fern-like leaves and grows to around 1 metre in height with deep roots in the ground. Common areas of weed growth include river banks, grasslands, construction sites and railways.⁴

What causes ragweed allergy?

The allergy is caused by the Ragweed pollen,the most common pollen compound is called Amb a1.⁵ At the beginning of August, Ragweed plants will begin to bloom and in mid-September, the pollen count is the highest. There are several factors that increase the production of pollen. They include warm temperatures, low humidity and slightly windy conditions and concentrations are highest during the morning.⁶

Once you are exposed to the pollen in the air, your immune system may develop an allergic reaction, making you sensitive to the pollen. The pollen can enter the body via touch, inhalation or ingestion. Once the pollen is inside the body, the immune system will become activated and IgE-mediated cells will produce a substance called histamine, which is responsible for the symptoms of a Ragweed allergy. If someone in your family has a ragweed allergy, then you are more likely to develop the allergy too, this is known as a predisposition.²

What are the signs and symptoms of ragweed allergy?

Common symptoms of ragweed allergy include: 

• Cough 
• Runny nose 
• Itchy throat and eyes 
• Sneezing 
• Watery and irritated eyes 
• Fatigue and weakness⁷

These common symptoms are similar to hay fever. They are caused by the inflammatory reaction when the nasal surfaces are exposed to pollen.⁶

Ragweed rash

• In some patients, a skin reaction may occur, usually due to contact with the Ragweed pollen. After 24 to 48 hours, individuals may present with itchy red streaks, which can eventually form blisters. The rash can persist for 2 to 3 weeks and usually self-resolves.¹

Severe symptoms of ragweed allergy include

• A flare-up of asthma symptoms: In asthmatic patients, inhaling the Ragweed pollen can cause spasms and inflammation within the lungs, which reduces the volume of air entering the lungs. This can cause symptoms like wheezing, shortness of breath, and a cough.¹

Oral allergy syndrome symptoms

• Patients with Ragweed allergy may also develop oral allergy syndrome. This is caused by the cross-reactivity between the proteins in certain foods and the Ragweed pollen, the immune system will then cause an allergic response physically, presenting as swelling of the lips, throat or mouth, and itchy and scratchy throat.⁸ 
• Foods that can cause oral allergy syndrome include melon, banana, mango, artichoke, cucumbers, peanuts, corn, sunflower seed and many more. ⁹

How is ragweed allergy diagnosed?

Medical history and physical exam

The initial method of diagnosing a Ragweed allergy is by taking a medical history and a physical exam. The doctor will be able to narrow down a diagnosis if the individual presents with hay fever-like symptoms occurring during the latter months of summer.²

Skin prick test

After conducting the initial medical history, the doctor will order a skin sensitivity test, also known as a skin prick test. A skin prick test uses a diluted form of the allergen and it is applied to the individual's forearm, the skin is then pricked with needles known as lancets.¹⁰ After 15 minutes, a positive result is if the skin produces a wheal which is a red raised itchy bump on the skin measuring at least 3 mm in diameter. The reaction is due to the cross-linkage of specific IgE that is found on mast cells. This causes degranulation and the release of histamine. This test offers the advantages of being rapid, inexpensive, and tolerable for the patient but also has contraindications. It cannot be used in patients with eczema, dermatographism, or urticaria with or without angioedema. Also, the skin prick test carries the risk of causing new sensitization to the Ragweed allergen.⁶

Blood tests

Blood tests can also be carried out to diagnose Ragweed allergy known as a ImmunoCAP Immuno-Solid phase Allergy Chip assay which is used to detect the Ragweed specific IgE antibodies in the blood. From this test, the IgE antibodies to the two major allergens Amb a1 and Amb a11 can be identified, and although other allergen antibodies can be found using this method, these are the only ones specific to Ragweed pollen. If a positive result is found from this test, Ragweed, immunotherapy may be considered. However, this method is less commonly used because it is more expensive.⁶

How is ragweed allergy treated?

Preventive measures 

Prevention is one of the options for reducing the number of Ragweed allergy cases per year. It involves reducing an individual's exposure to the allergen and methods include: 

• Keeping windows and doors securely closed to reduce levels of pollen inside
• Wear a mask when outside so that airborne pollen can not enter through the nose
• Avoid staying outdoors during times when the pollen count is the highest (during the late summer, in the morning or on warm windy days)
• Change into different clothing and take a shower after being outdoors
• Monitor local pollen counts daily
• Dry-washed clothes inside rather than outside
• Use antihistamines or a saline nasal spray prior to exposure to the Ragweed allergen^1,4

Over-the-counter (OTC) medications

Relief from the symptoms of Ragweed allergy can be through over-the-counter medications, including antihistamines and anti-inflammatory nasal sprays. Common antihistamines include; 

Loratadine, Cetirizine and Fexofenadine act to reduce the congestion within the nasal passages. It is recommended to take these before the start of your symptoms when the pollen count is high. It is important to be aware that some of the antihistamines may cause drowsiness as a side effect.¹¹

Decongestants may also be purchased to help reduce nasal congestion and include pseudoephedrine or oxymetazoline  However, they may worsen high blood pressure or heart problems, so should be used with caution.²

Prescription medication

If the over-the-counter medication does not provide enough relief or symptoms continue to persist, then prescription drugs may be used as an alternative. This includes steroids such as prednisolone or for itchy eyes, loteprednol eye drops can be used. Although these may be good for symptom control, they may take a longer time to work.²

Immunotherapy

Immunotherapy is a method for those with moderate-severe persistent symptoms of Ragweed allergy and is also useful for patients at risk of developing more severe asthmatic symptoms. It works by increasing an individual's tolerance to the Ragweed allergen in order to reduce or eliminate their symptoms. It is a form of long-term management for the allergy and can be prescribed as injections or sublingual tablets.¹ 

With injections, a patient is given one or multiple allergens within one injection, and this is administered once a week. It helps to build resistance against the allergen. 

For the sublingual form, tablets that dissolve under the tongue are given daily. They work in the same way to build tolerance but must be started 12 weeks before allergy season. 

This is a long-term treatment plan and may take months to years before the body can build tolerance and reduce the response of the immune system to the Ragweed pollen. This is why it is considered a more expensive approach in the short term.¹²

Summary

Ragweed Allergy is a common allergy that many individuals experience worldwide. It can cause an immune reaction, displaying symptoms such as a cough, runny nose, itchy throat and eyes and in more severe cases can lead to flare-ups of asthma.⁷ One additional effect of a Ragweed allergy is its association with oral allergy syndrome, whereby due to cross-reactivity between the proteins in certain foods and the Ragweed pollen, patients may develop an allergic reaction to certain types of food.² A doctor will diagnose the Ragweed allergy via medical history and physical exams and will conduct a skin prick test. 

A skin prick test measures the sensitivity of an individual to the Ragweed pollen and blood tests can also be used as a more expensive alternative method.⁶ Lastly, to treat this allergy, prevention is key in order to reduce pollen exposure. Over-the-counter medications like antihistamines and nasal sprays are also useful for reducing symptoms. 

Prescription medication like steroids may also be used for a Ragweed allergy but they may take longer to control the symptoms. Immunotherapy is also used in the form of injections or sublingual tablets to help patients build tolerance to the Ragweed allergen. Treatment and the course of a Ragweed allergy is specific to each individual, so it's important to consult a healthcare professional to find the best management plan for yourself.¹