Prevention is your first line of defense
Preventing bites from mosquitoes and ticks is the best defense in avoiding the transmission of diseases such as Zika and Lyme. A combination of chemical repellents, creating barriers with clothing, reducing tick and mosquito populations in your own yard, and careful inspection and cleaning after excursions outdoors is your best bet. Before developing a plan of defense, learn what the risks are in your area and consider your exposure risk. A person hiking in deep woods for hours requires different preventative measures then a person who’s relaxing in their back yard (and yes, even your back yard can be a source of exposure).
Options for insect repellents
One of the most effective ways to prevent tick and mosquito bites is to repel insects with the use of a chemical insect repellent.
DEET (NOT RECOMMENDED) is a widely used and studied insect repellent which has been in use since 1954. It has been shown to be effective in repelling both mosquitos, ticks and other biting insects. It’s also the most controversial insect repellent due to concerns about odor, its greasiness, its ability to melt plastic and its neurotoxicity. Although, in adults, skin reactions are the most commonly-identified potential side effect, neurological symptoms such as seizures are reported in infants exposed to DEET demonstrating that DEET can reach the central nervous system. Studies in mammalsare highly suggestive that adverse effects mimic many of those effects in insect, including altered balance, degeneration of neurons and cardiovascular changes. For these reasons, we do NOT recommend DEET unless the risk of exposure is severe. DEET should never be used in infants or during pregnancy.
Fortunately, there are some good alternatives to DEET that we do recommend. Since nothing is completely free of side effects, these should be used carefully, according to the label directions, and only for the duration that you need them.
Picaridin was developed in the 1980’s to mimic piperine, a compound found in black pepper. It has been used in the United States since 2005, but was widely used previously in Europe and Australia. It has been shown to be as effective as DEET in repelling mosquitoes, and will also repel ticks. Picaridin is odorless, non-greasy, and does not melt plastic. Less side effects have been seen in picaridin than in DEET, and there also seems to be less concerns about using picardin with children over 6 months.
IR3535 has been shown to be effective at repelling both mosquitoes and ticks. It has been used for more than 30 years in Europe. The French government recommended its use in Southern France during and outbreak of Chikungunya to children and pregnant women. The CDC also recommends its use for protection in areas with high risk of Zika virus exposure.
Permethrin is an insecticide that isn’t applied directly to skin but can be applied to clothing, shoes and bags, and will last through several washes. Permethrin is neurotoxic to insects including ticks, causing muscle spasms, paralysis, and death when insects eat or touch the chemical. Clothing can be purchased pre-treated, or permethrin can be applied at home. There are also companies that will treat your clothes for you. If you treat your clothes at home, it should be done outside, and care should be given to avoid inhalation and coming into direct contact with the chemical. According to the EPA, permethrin treated clothing is safe for use in pregnant women, although evidence is thin and some animal studiessuggest potential for harm. To reduce risk of overexposure, wash Permethrin-treated clothing as well as clothing that has been sprayed with other insect repellents separately from non-treated clothing.
Oil of Lemon Eucalyptus* is a refined extract from an Australian eucalyptus tree. P-Menthane-3,8-diol (PMD) is the active compound. PMD is registered with the EPA as a biochemical pesticide effective against both ticks and mosquitoes, and has been shown to be as effective as DEET in similar concentrations but at a lesser duration. Oil of Lemon Eucalyptus (the trade name for the refined oil) should not be confused with lemon eucalyptus oil (an essential oil). Though lemon eucalyptus oil has some PMD, Oil of Lemon Eucalyptus is refined to increase the concentration of PMD. Oil of Lemon Eucalyptus is not recommended for use in children under the age of 3.
Oil of Citronella* is derived from lemongrass, and has been used for more than 50 years as an insect and animal repellent. It is volatile and requires reapplication hourly. It is not effective against ticks, but is effective against mosquitoes, house flies and fleas. Oil of Citronella is not recommended for use in children under the age of 6 months.
Nootkatone* is an aromatic compound found in grapefruit skins. Studies have shown that it is highly effective at repelling ticks and is currently undergoing testing for its ability to repel mosquitoes carrying Zika. Nootkatone (from evolva) is currently in R&D, and is awaiting EPA approval which is expected in the second half of 2018.
Oil of Nepeta cataria* is an oil extracted and refined from the catnip plant. Nepetalactone is the active compound and has been shown to be very effective at repelling mosquitoes. It is also the compound that cats are drawn to in the catnip plant.
*Challenges with using essential oils
Concerns regarding neurotoxicity and the unknown long term side effects of using chemical repellents has led to increased interest in natural repellents. Plants and plant extracts such as essential oils have been used for centuries to repel insects, including oil extracts of lemon eucalyptus, citronella, grapefruit and catnip listed above. But are they as effective and safer than synthetics?
Essential oils are lipophilic extracts from plants that contain many compounds that produce aromas. They have been used for centuries for their medicinal properties. Essential oils are generally recognized as safe (GRAS), but can be contraindicated when taking certain medications, in people with certain health issues, in women who are pregnant, and in children. In some cases, essential oils can cause rashes and skin irritation, respiratory issues, and headaches. Essential oils can have strong, and sometimes unpleasant, odors. For use directly on the skin, many essential oils require dilution in a carrier oil to prevent irritation, and some increase photosensitivity.
One of the biggest challenges using essential oils as an insect repellent is that they are extremely volatile and so will evaporate quickly, requiring frequent reapplication to remain effective. Also, each essential oil tends to repel only certain insect populations. One type of mosquito may be deterred by one essential oil, but another mosquito may not mind it. Reviews of plant-based insect repellents from 2011 and 2014 provide an overview of essential oils tested as repellents for specific insect populations.
Things to consider when selecting & using an insect repellent
When selecting an insect repellent, learn what the risks of exposure are for your area, and then check to make sure the product you’re using is approved with the EPA to repel those pests. Read the label carefully, even on botanical insect repellents, and pay close attention to instructions for application, safety warnings, and duration of effectiveness. Products that combine insect repellents with sun screen may require frequent reapplication to maintain effectiveness of the sunscreen and may therefore increase the risk of overexposure to the repellent; so consider using separate products. If you have health issues, are pregnant, or have small children, you may want to consult with your practitioner about how to safely reduce the risk of exposure to tick- and mosquito-borne illnesses in your area.
Some products, such as DEET, dissolve plastics so use caution when spraying on backpacks, eyeglasses, watch bands, and plastic containers. Avoid spraying near food, and always wash your hands before handling food. Repellents should only be applied to clothes and exposed skin free from cuts or wounds. Spray repellents should be applied outdoors, never inhaled, and never sprayed directly in the face.
Children should avoid handling or applying insect repellent unless you’re certain your child can do so safely. When applying insect repellent to children, first apply to your own hands and then apply to your child. Insect repellent should not be applied to a child’s hands because of the higher risk of accidental ingestion.
Creating a barrier with clothing
Wearing long sleeved shirts tucked into long pants and tucking your pants into socks helps to create a barrier to prevent insects from getting into and under you’re clothing. Wearing light-colored fabrics helps make insects more visible on your clothes, and easier to remove. Clothing also reduces the amount of exposed skin treated with repellent reducing direct exposure. Tuck hair under a hat that has a wide brim to protect head, neck and shoulders. If working in the garden, wear gloves with sleeved tucked in.
Keeping pests out of your home
Once you’ve had your fun outdoors, there are a few things you can do to help further reduce the risk of bites and reduce chemical exposure. After coming indoors, Mary Beth Charno, APRN-C, Lyme Disease expert In the Hudson Valley NY, recommends removing clothing as soon as possible, and if you’ve been to tick-infested areas, place your clothes in the dryer for 15 minutes on high before washing. Shower as soon as possible using a washcloth in a gentle rubbing motion to help remove small ticks or insects that may be on your skin but might not be visible. Inspect each person to look for bites or ticks that have attached and need to be removed and inspect gear and pets to make sure no pest has hitched a ride home.
Things you can do in your own habitat
Reducing tick and mosquito populations around your home can also help reduce your risk of exposure and make hanging out in your own back yard worry-free.
To reduce mosquitos, remove areas where mosquitoes like to live such as places with standing water. This can include removing old toys, wheelbarrows, buckets, etc., and changing water frequently in things like bird baths. Screens on windows and doors can help stop these critters from entering your home. Certain plants repel mosquitoes including lavender, marigolds, rosemary, basil, geraniums and of course catnip and lemongrass which are easy to grow at home.
For ticks, thoughtful landscaping choices can help reduce populations. Ticks like tall grasses and brush. Try removing these from areas near the house or near the edges of your lawn. Keeping the lawn mowed and raked free of grasses and leaves is helpful. If your lawn or play area backs up to the woods, consider creating a 3 food wide buffer using wood chips or gravel to reduce the migration of ticks. High fencing can discourage deer from entering your yard, carrying ticks. Help reduce the rodent population that ticks often feed on (chipmunks, mice, etc.) by neatly stacking wood piles in a dry area and keeping your yard free of debris.
Tick tubes are another way to reduce tick population in your yard. Tick tubes are essentially a tube filled with cottons balls soaked in an insect repellent, typically permethrin, and placed around your property. Rodents like the cotton balls as nesting material and take the treated cotton balls back to their homes. Once the permethrin-soaked cotton balls make their way back to a nest, the rodent becomes covered in the insecticide and kills any ticks that try to feed on it. The results of tick tube studies have been mixed, but it may take time to sufficiently reduce tick populations noticeably. Damminix and Thermacell are two commercially available tick tubes. You can also make your own tick tubes, and should be made outdoors using gloves, eye protection, and mask to prevent over exposure to the repellent.
The importance of a healthy diet & lifestyle
Being outdoors is an important to a healthy lifestyle. Sun exposure is required for vitamin D synthesis. Many outdoor activities such as hiking, cycling, playing sports, and working in the garden are excellent forms of exercise, and being out in nature has been shown to reduce blood pressure, improve mood, decrease anxiety, and improve sleep.
While repellents and barriers help prevent illness from outside our bodies, diet and lifestyle help prevent illness from inside our bodies. Keeping inflammation at bay and our immune system in balance allows our body’s own defenses to fight off infective agents. When nutrient replete and with sufficient antioxidants, our bodies also have the ability to break down toxins like those found in insect repellents through detoxification pathways (note that individuals with single nucleotide polymorphisms in their detoxification pathways may have an impaired ability to eliminate toxins including from repellents, and so should be more judicious in their choice of repellent and can ramp up nutrient support for their detoxification pathways).
The following are some basic suggestions to help support immune function and detoxification.
Stay hydrated – Water is needed for many of the phase I detoxification reactions, and to excrete toxins out of the body.
Eat adequate protein – Several amino acids are needed for phase II detoxification reactions that render the potentially toxic metabolites from phase I detoxification reactions inert.
Avoid inflammation-causing foods – Processed foods or food sensitivities can cause inflammation in the gut causing the junctions between the cells that line the gut to weaken letting food particles leak out and confuse the immune system.
Get outdoors – Before it is activated in the liver and kidneys, vitamin D is synthesized in the skin with exposure to sunlight. It is a key nutrient for healthy immune function.
Eat lots of colorful vegetables and fruits – Plant-based foods contain a variety of nutrients and compounds used in biochemical processes throughout the body. These foods contain antioxidants that neutralize free radicals that can cause oxidative stress, have nutrients like B vitamins used in both energy production and detoxification, nutrients like vitamins A and vitamin C that are vital to proper immune function, and phytonutrients like curcuminoids and sulphur-containing compounds that are vital for detoxification.
Include omega-3’s in your diet – These fats help support immune function and reduce inflammation.
The following sites are good resources for more information about this topic.
The Environmental Working Group (EWG) discusses the use of insect repellents in this article.
This article was contributed by Dorie Passen MS, nutrition resident with Dr. Kara Fitzgerald. Dorie holds a Master of Science degree in Nutrition and Integrative Health from the Maryland University of Integrative Health. Her lifelong passion for food and cooking is the underlying inspiration for her food-as-medicine approach to nutrition. Previously, Dorie has worked in the fields of electrical engineering and construction, holds an additional Master of Science degree in applied mathematics, and has published research in percolation theory. Dorie is so very grateful for this opportunity to be part of the Functional Nutrition Residency Program, and to work and learn alongside the practitioners at the clinic of Dr. Kara Fitzgerald.