An alternative to allergy shots, sublingual immunotherapy (SLIT) can provide relief from symptoms of some common allergies. 

What is sublingual immunotherapy?

Allergy immunotherapy is an allergy treatment that works by exposing the person to small doses of an allergen (a substance that produces an abnormal immune response). Sublingual immunotherapy is a relatively new approach to delivering allergy immunotherapy — the medicine is placed under the tongue (sublingually) instead of injecting it under the skin (subcutaneously, with allergy shots).

The dose is gradually increased so that over time, it lowers the sensitivity and increases immunity (tolerance) to the allergen. This treatment can slowly help reduce the severity of symptoms and frequency of allergy attacks. 

Many people with allergies to airborne substances have allergic reactions affecting the eyes (allergic conjunctivitis), nose (allergic rhinitis) and lungs (allergic asthma). Most people use antihistamines, decongestants, nasal sprays and inhalers to treat these symptoms. Allergy immunotherapy has been very effective in addressing these symptoms and helping reduce reliance on allergy medications.

Sublingual immunotherapy is delivered as allergy drops and allergy tablets placed under the tongue.

Sublingual Allergy Drops Versus Tablets

SLIT allergy tablets are approved by the FDA and are covered by most insurance plans. However, at this time, the tablets can be used only for the following airborne allergens:

• Short ragweed pollen
• Grasses (sweet vernal, orchard, perennial rye, timothy and Kentucky bluegrass)
• House dust mites 

The other form of SLIT, allergy drops, is not currently approved by the FDA for treating allergies and is not covered by insurance. Allergy drops have been used in Europe for years, and their “off-label” use in the U.S. is increasing.

Allergy drops offer an important benefit: They address a broader range of airborne allergens and are customized for each patient. Based on the patient’s allergy test results, the physician can formulate a mixture that can include such allergens as:

• Trees
• Grasses
• Weeds, including ragweed
• Cats and dogs
• Molds
• Dust mites
• Feathers

Sublingual Allergy Drops Versus Allergy Shots

Sublingual allergy drops are made from the same raw materials as those used in allergy skin tests and allergy shots. The FDA has long approved these extracts for allergy testing and shots, but they are not currently approved for SLIT.

Allergy shots have been used for a long time to treat rhinitis, conjunctivitis, asthma and bee venom allergy. Shots are somewhat better than drops for treatment of allergic rhinitis and asthma, with laboratory tests more likely to show favorable immune changes compared to drops. 

Allergy shots must be given in a doctor's office under observation so that possible adverse reactions can be treated. Allergy shots are the right choice for many people, but for others, sublingual immunotherapy offers more comfort and convenience, as well as greater flexibility to travel without the need to return to the clinic for shots.

Who can benefit from sublingual immunotherapy?

SLIT allergy drops can be part of a treatment plan for children and adults who have allergies (including allergic rhinitis/conjunctivitis or asthma) that are confirmed by positive allergy skin or blood tests. Multiple allergies can be treated with SLIT drops at the same time.

People who take beta blockers and those who have labile asthma are rarely candidates for SLIT. 

Your doctor will evaluate your medications and your overall health to determine if SLIT is safe and effective for you. The treatment is tailored for each person’s allergies, medical conditions, response to previous allergy treatments and lifestyle.

Can pregnant women take allergy drops? 

It is not recommended for pregnant women to start taking allergy drops. However, if a woman is already taking sublingual immunotherapy drops and becomes pregnant, she can continue SLIT at a stable dose throughout pregnancy.

How do I take sublingual immunotherapy drops?

If your doctor recommends allergy drops, a custom solution will be prepared for you in dropper vials. Your customized drops will be in one, two or three vials, according to the number of things to which you are allergic.  

Sublingual immunotherapy drops are taken once per day by placing the drops under your tongue for two minutes, then swallowing. Your doctor will instruct you on the proper technique. Caregivers need to give the drops to young children.

SLIT drops taste sweet because they contain glycerin, and most people are comfortable with the taste. To improve the treatment’s effectiveness, do not eat or drink for 15 minutes before and after taking the drops.

During the first 10 weeks, called the escalation or buildup phase, your daily dose gradually increases from diluted to full strength. Therapy then shifts to a maintenance phase, during which you start taking the same dose each day. You will have regular follow-ups with your allergist to assess the effects of the sublingual immunotherapy and to adjust the dosing as needed.

How should I store allergy drops?

It is best to keep the allergy drops in a place that reminds you to take your daily dose. Each 10-milliliter dropper vial lasts about 10 weeks, and the formula is designed to remain potent without refrigeration during that time, although refrigeration does no harm. If you order two or more vials, you may want to refrigerate (being careful not to freeze) the vials that will be used later.

How long does sublingual immunotherapy take to work?

Most people note an improvement in their allergy symptoms in three to four months when they take allergy drops daily as directed. To confirm it is working as intended, the doctor will schedule a follow-up for about six months after treatment starts. 

Some doctors recommend start times for certain allergies, so that sublingual immunotherapy can prepare the patient for the seasons when the allergen is likely to be more of a problem. For example, patients who have grass pollen allergies may be instructed to begin therapy in the winter so they are better protected in the spring. At Johns Hopkins, our approach is to give SLIT year-round to continue training the immune system.

It takes a long time to safely train the immune system not to overreact to an allergen. Daily dosing with sublingual immunotherapy may continue for three to five years.

Can I fly with allergy drops?

Yes, you can fly while taking sublingual immunotherapy drops. Your doctor will provide a letter allowing you to carry the drops on an airplane.  

Is sublingual immunotherapy safe? 

Sublingual immunotherapy is safe for both adults and children, as confirmed by numerous studies during the past 10 years. The World Health Organization has endorsed SLIT as an alternative to injection therapy (allergy shots). 

Dangerous allergic reactions (such as anaphylaxis) are very rare with sublingual immunotherapy, and no fatalities have been reported to date. Mild to moderate allergic reactions are possible.

Do not use sublingual immunotherapy if you have open sores, cuts or ulcers in your mouth, or if you are undergoing dental procedures that cause bleeding (oral surgery, tooth extraction, etc.), because the allergen in the medication could enter your bloodstream too quickly and cause a reaction. You can resume taking the tablets or drops when your mouth has healed. 

If you have a severe allergic reaction at any time (such as difficulty breathing, a sensation of throat closure or if you feel as if you will lose consciousness), use the EpiPen (adrenaline auto-injector) and call 911 immediately. Your allergist will prescribe an EpiPen and teach you how to use it in case of a severe reaction.

Sublingual Immunotherapy Side Effects

Some people notice mild swelling or itching of the lips, tongue and throat during the first couple of weeks after starting sublingual immunotherapy. If you have any of these reactions, tell your doctor. In most cases, these symptoms decrease over time as you continue taking sublingual immunotherapy. 

Moderate side effects have been documented (for one in about 10,000 doses), including:

• Lip, mouth and tongue irritation
• Nausea, vomiting, abdominal cramping and diarrhea
• Itching or redness of the eyes
• Nasal symptoms (sneezing, itching or congestion)
• Increased severity of asthma symptoms
• Skin reactions (hives, itching or swelling)

Another rare side effect is an allergic reaction in the esophagus — the tube between the mouth and the stomach. This problem (eosinophilic esophagitis) can feel like heartburn or difficulty swallowing.

How much do allergy drops cost? Are they covered by insurance?

Because SLIT allergy drops are not currently approved by the FDA, insurance does not cover the cost, which varies from clinic to clinic. The cost of a one-year supply of allergy drops ranges from $1 to several thousand dollars, depending on the number of things to which you are allergic. In addition to obtaining the drops, you will need follow-up office visits that will be covered depending on your insurance plan. If you have a health savings account (HSA), find out if you can use it for these expenses.

It is important to understand this financial commitment before starting use of allergy drops — the full course of treatment often lasts three to four years.