Better Safe Than Sorry: Insect Repellents in the Age of Zika

In All, Consumer products by Keri Szejda

Article by Dr. Keri Szejda of the Center for Research on Ingredient Safety and the Risk Innovation Lab at Arizona State University and Dr. Diana Bowman of the Risk Innovation Lab and Sandra Day O’Connor College of Law at Arizona State University.

Avoid travel to outbreak areas. Wear long-sleeved shirts and pants. Mosquito proof your home. Use insect repellant. Avoid sex or use condoms.

To many, these oft-repeated United States (US) Centers for Disease Control and Prevention (CDC) guidelines for preventing Zika may just seem like common sense. But to pregnant women—who have more at stake as the mosquito-borne virus spreads, and also face a myriad of pressures about what to do and what not to do while expecting—the measures may not seem so feasible to follow, in every case, and every time.

Image credit: Centers for Disease Control and Prevention

Image credit: Centers for Disease Control and Prevention

 Zika Infection Poses Severe Threat to Babies in Utero

Although there is still much that public health officials and scientists don’t know about the virus, we do know that the dangers for pregnant and soon-to-be pregnant women are real. Very real. For most of us, contracting the Zika virus may only mean a mild fever or rash, if any symptoms at all. Earlier this year, however, the CDC definitively linked those infected with Zika during pregnancy with a higher risk of having a baby with microcephaly—the condition where infants are born with abnormally small brains and heads—and other severe birth defects. We’ve already seen the tragic images coming out of countries such as Brazil, where Zika has been connected with thousands of cases of babies born with microcephaly in the last year. These infants require higher levels of care and may have developmental delays, intellectual disabilities, seizures, and hearing and vision losses that will last their lifetimes.

So far in the continental US, cases of local mosquito-borne Zika transmission have only been confirmed in Miami-Dade County. All other cases come from travel to more southerly destinations or through sexual transmission (another significant vector of the disease). The range of the Aedes mosquitos, primarily responsible for carrying Zika, extends much farther, and states along the Gulf Coast are thought to be particularly vulnerable to future localized outbreaks. (And that’s not even counting the 8,746 locally-transmitted cases in Puerto Rico.) For many American women who are pregnant, or who hope to become pregnant, questions regarding safety, risks, and trade-offs are getting very real. Very fast.

CDC Advice to Avoid Contracting Zika

As the potential risk of Zika-infected mosquitos rises in the US, federal, state, and local governments have mounted active campaigns to raise awareness about transmission. But although their advice about taking steps to protect yourself from mosquito bites and sexual transmission of the virus is entirely valid, it’s worth talking about how the advice is being communicated, and whether women are willing—and able—to take all of the recommended steps. The CDC has clearly stated what we do and do not know about the virus and made recommendations about steps to take to prevent transmission. The CDC hasn’t, however, crafted tailored, nuanced messages that address the real-life concerns and personal circumstances of pregnant women. Or those women who hope to become pregnant within the next 12 months.

Take, for example, the CDC’s suggested measures for preventing mosquito bites. They advise wearing long sleeves and pants. It’s entirely reasonable in some areas. But if you live in hot and humid climates—and it is worth doing a mental overlay map of places where Aedes mosquitos thrive and average temperatures in August—it’s a lot to ask. Especially for pregnant women, who run hotter than most.

Woman spraying insect repellent on skin

Pregnant women are advised to do everything they can to prevent mosquito bites.

To DEET, or Not to DEET?

For exposed skin, such as face and hands, the next dilemma appears: to DEET, or not to DEET? The CDC communicates clear guidelines on this: Use one of four EPA-registered insect repellants (those with DEET, Picaradin, IR3535, and oil of lemon eucalyptus or PMD as active ingredients) as directed, and know that they are proven safe and effective for pregnant and breastfeeding women. For many expecting parents, however, simple “use as directed” and “trust us, it’s safe!” messaging is likely to be inadequate. Why? Because while it may be right, and reflect the state of the science, it doesn’t create trust. Nor does this response adequately take into consideration the broader non-scientific dimensions that are likely to be of importance to those asking the question.

In today’s better safe than sorry” and “bubble wrap” approaches to risks during pregnancy, there’s a lot of conflicting and confounding information about what is and isn’t safe for mom and baby, especially early in a pregnancy. Everyone—scientists, health professionals, family members, and even passing strangers—seem to have an opinion about what pregnant women should and shouldn’t be doing with their bodies. And of course this freely given advice is sometimes solicited, and sometimes not. Sometimes the advice is grounded in scientific validity, and many times not. Take alcohol, for example. Women are advised to avoid even a sip of wine—and risk public shaming if they partake—but research seems to more realistically support the safety of light alcohol consumption. Potential danger seems to lurk in every medication, every plastic water bottle, even food. So when a parent-to-be considers whether to wear insect repellent, it’s easy to see how concerns about its chemical contents may cause someone to think twice about a passing assurance that it’s “safe”.

To be clear, if you are pregnant and living in an active Zika transmission zone, or even an area with a dense mosquito population, using repellant is a sensible choice. But the directive leaves unanswered the kinds of questions that many concerned parents are prone to ask. When used as directed, the research does support the conclusion that using approved insect repellents is safe (see EPA and Agency for Toxic Substances and Disease Registry statements). An individual’s biggest concern is likely to be skin irritation. For excessive use or unintended exposure—and by this we mean dousing yourself in the spray or eating the stuff—neurological effects in adults and children, including seizures, are possible. Albeit highly unlikely.

As for pregnant women and their unborn children, the same seems to hold true. Though, considering this is the population that public health officials are currently trying to target for the regular use of repellents, it is unsettling that only cursory safety statements are offered. For this group, information backing up safety reassurances are likely to be of critical importance.

Due to the complicated ethics of conducting research on pregnant women, there hasn’t been a lot of research on the use of insect repellants during pregnancy. However, we do have two available studies that provide information on the health of human infants who have been exposed to DEET, the most commonly used chemical in repellents, in utero. In a double-blind, randomized trial, newborn babies exposed to DEET during the second and third trimesters of pregnancy did not show any adverse growth effects at birth. Nor did they show any adverse developmental effects at age one. Another study found that the presence of DEET in maternal blood and newborn cord blood was not associated with adverse newborn growth outcomes. The results from these two human studies, as well as studies of pregnant animals and their offspring, are reassuring. In sum, the research suggests that DEET, at least under typical daily use during the second and third trimesters of pregnancy, does not negatively impact fetal growth or development.

But there’s an absence of data during the first trimester of pregnancy—which is problematic because exposure later in pregnancy is not necessarily translatable to early exposure. The first trimester is the time period when agents (technically known as teratogens) are most likely to cause damage to the fetus—alcohol, tobacco, and Zika. And so while the body of research largely supports the safety of DEET and other types of insect repellents during all stages of pregnancy, there are still some unknowns. This means that not everyone will feel comfortable spraying up at all times, under all conditions. And here, in the age of the Zika virus, is the crux of the real-life decision-making women and their families are now facing: assessing potential risks, benefits, and trade-offs with incomplete information.

Woman Contemplating Pregnancy Risks

Decision-making during pregnancy often requires assessing potential risks and trade-offs .

Can the Public Health Strategy Include Individual Risk Assessments?

Generally speaking, the use of fear appeals can be an effective public health communication strategy. Specifically, fear appeals are effective when they identify a severe threat that is likely to occur and then suggest an easy solution.

The CDC offers a clear and simple message designed to promote the use of insect repellents:                                

“Warning: Zika is linked to birth defects…Use insect repellent. It’s safe and it works! Read the label and follow the directions.”

Sound advice. It begins to unravel, however, because we know that the perception of ease, feasibility, and safety will vary considerably when these blanket recommendations meet real-life individual circumstances, including the likelihood of acquiring Zika. Just look at some online pregnancy forums. What if the woman doesn’t live in an active transmission zone? What if she, of more sensitive pregnancy stomach, gets nauseous from the smell of the insect repellant? Should she skip her best friend’s wedding in Puerto Rico? What about the work trip to Florida? Should her sexual partner avoid travel, too? We’ve now firmly landed in a zone of uncertainty where we just don’t know what “safe” really means.

With Zika, decision-making involves assessing potential risks and trade-offs, and many women will prefer to evaluate their own comfort level in relation to Zika and the use of DEET rather than mindlessly following rigid CDC recommendations. In this way, there’s a case to be made for more nuanced, less paternalistic approaches to these public health campaigns.

Public health messaging is often more effective in promoting behavioral change when it’s tailored to individuals. For example, this could involve encouraging women wary of chemical contact during the first trimester to consider at least using repellents if they travel to high-risk areas, in conjunction with protective clothing, rather than not using repellent at all. Or for women who want to reduce DEET exposure, using an extended-release spray with a lower concentration (20-30%) of the chemical can be just as effective as higher concentrations. These suggestions could come in the form of FAQs that target specific concerns.

But messages don’t have to be static, either. For instance, interactive websites can offer tailored information based on individual answers to a series of questions. The Environmental Working Group has taken a step in this direction, with a Guide to Bug Repellents in the Age of Zika. Here, individuals can click and access information that is most relevant to them, such as “I’m pregnant and need Zika protection” and “I’m pregnant and bug-borne diseases are rare where I live”.

With something as personal as pregnancy, especially in our modern times where women are bombarded with all sorts of conflicting better-safe-than-sorry dictates, we know many women will seek factual information and will prefer to make their own informed decisions based on their differing circumstances. Effective guidance has to take this complexity into account.

Public health messages make an important contribution to society, helping individuals to make extremely important, and often very personal, health decisions. And these decisions often impact not only themselves, but family members and the community at large. In the face of complex health decisions such as those surrounding Zika, factual, yet nuanced, messages will aid women in making their own informed decisions.