Stick on anti-radiation protection shields etc are often made of metal which may block signal and prevent reliable mobile phone communications with signal towers. Mobile phones recognise the potential for a dropped signal and actually increase power to compensate. The result is a fast draining battery and an even higher radiation output as a result of using the product (an exception to this are shields that are placed in between the phone and the user as these do not impede signal to cell towers to any significant degree)

A carrier wave oscillates at 1900 megahertz (MHz) in most phones, which is mostly invisible to our biological tissue and doesn’t do damage. The information-carrying secondary wave necessary to interpret voice or data is the problem, says Dr. Carlo. That wave cycles in a hertz (Hz) range familiar to the body. Your heart, for example, beats at two cycles per second, or two Hz. Our bodies recognize the information-carrying wave as an “invader,” setting in place protective biochemical reactions that alter physiology and cause biological problems that include intracellular free-radical buildup, leakage in the blood-brain barrier, genetic damage, disruption of intercellular communication, and an increase in the risk of tumors. The health dangers of recognizing the signal, therefore, aren’t from direct damage, but rather are due to the biochemical responses in the cell.

The only sure way is to stop using a cell phone. Most people however would prefer to play safe by simply reducing their exposure to radio frequency radiation. Bluetooth devices emit only 10% of the radiation of a cell phone. A hands-free set enables the user to keep the phone away from the head but usually leaves the phone near some other part of the body. It is safe to say that in the event that radio frequency radiation causes damage, you would like to protect other parts of your body. Therefore the only way to reduce your risk is to reduce the radio frequency radiation your body absorbs. SAR Shield reduces radio frequency radiation by up to 89%. 
The guidelines created a measure of the rate that body tissue absorbs radiation during cell phone use called the specific absorption rate (SAR). The SAR for cell phone radiation was set at a maximum of 1.6 watts of energy absorbed per kilogram of body weight. The limit was set due to the thermal effects of cell phone radiation (all RF radiation can heat human body tissue at high enough levels) - it was not set to mitigate other biological effects cell phone radiation might have such as DNA damage or cancer.

Wow so glad I read this article tonight. I have been suspicious of my tablet and phone and in my car – I was experiencing tingling and some irregular pain in odd areas of the body. When I was in my car is when I noticed it – then I realized the same thing would happen when I was reading on my tablet. I just had the discussion with my husband as the body does have an electrical field around it the EMP’s are interrupting that field and damaging the body., which is exactly what I suspected. I also recently read an article that two college girls conducted a “test” project they put a cell phone in one room with and tray of seedlings in soil and put the same tray in another room, very carefully monitoring both room with the exact same temperatures etc. And I believe they let the plants grow for over a week. In the room with the cell phone the seeds had not even sprouted and in the room without the cell phone the seed sprouted and the plants were at least and inch in growth – that is a simple but proven test that cell phones interrupt cellular growth and damage cells. Thank you to all who commented here. I do have to look up what is EHS. Also have to get this info to my daughter who gets headaches.
Independently tested DefenderShield technology uses a patent-pending sophisticated layering of separate non-toxic, human safe materials processed for maximum radiation blocking efficiency. Each material has unique and targeted radiation shielding characteristics designed to work in unison to up to eliminate all radiation emissions from 0 to 10 GHz.
Dr Davis holds a B.S. in physiological psychology and an M.A. in sociology from the University of Pittsburgh, 1967. She completed a PhD in science studies at the University of Chicago as a Danforth Foundation Graduate Fellow, 1972 and a M.P.H. in epidemiology at the Johns Hopkins University as a Senior National Cancer Institute Post-­Doctoral Fellow, 1982. She has authored more than 200 publications and has been published in Lancet and Journal of the American Medical Association as well as the Scientific American and the New York Times.
Don’t rely on a “radiation shield” or other products claiming to block RF energy, electromagnetic fields, or radiation from cell phones. According to the U.S. Federal Trade Commission, products that interfere with the phone’s signal may force it to work harder and emit more RF energy in order to stay connected, possibly increasing your exposure. It is best to use wired solutions to reduce RF rather than rely on an untested  product.
But he cautioned that the exposure levels and durations were far greater than what people typically encounter, and thus cannot “be compared directly to the exposure that humans experience.” Moreover, the rat study examined the effects of a radio frequency associated with an early generation of cellphone technology, one that fell out of routine use years ago. Any concerns arising from the study thus would seem to apply mainly to early adopters who used those bygone devices, not to users of current models.
Well, either the sleeve blocks 99.9% of all emissions or it doesn’t. The point is, anything less than what the company is advertising constitutes FRAUD. If they had said a 50% reduction would be seen, then the RF meter should have reflected that. Methinks that this company is duping a lot of customers. While the product ‘looks’ good, my experience was that it made NO difference at all. In fact, it was worse having this case and the notion of false security. I ended up getting horrific migraines right after I started using it. I was falsely confident that I was being protected. Perhaps part of the case blocked the signal which forced the phone to work that much harder, therefore nullifying any benefit. Please note, consumers. I would not recommend SafeSleeve based on my experience.
Protect your brain from RF (radio-frequency) pollution with this handsome baseball style hat. Specially designed to shield the head from frequencies from below AM through microwave, including cellular phone frequencies. Lined with sophisticated Staticot fabric woven from ployester/cotton with an ultrathin stainless steel fibers excellent radiation protection. This gives this unique fabric a truly comfortable, natural feel and the durability and washability of cotton, but with exceptional reflective characteristics. 

Cell-phone designs have changed a lot since the studies described above were completed. For example, the antennas—where most of the radiation from cell phones is emitted—are no longer located outside of phones near the top, closest to your brain when you talk, but are inside the phone, and they can be toward the bottom. As a result, the antenna may not be held against your head when you’re on the phone. That’s important because when it comes to cell-phone radiation, every milli­meter counts: The strength of exposure drops dramatically as the distance from your body increases.

The NTP studied radiofrequency radiation (2G and 3G frequencies) in rats and mice (33, 34). This large project was conducted in highly specialized labs that specified and controlled sources of radiation and measured their effects. The rodents experienced whole-body exposures of 3, 6, or 9 watts per kilogram of body weight for 5 or 7 days per week for 18 hours per day in cycles of 10 minutes on, 10 minutes off. A research overview of the rodent studies, with links to the peer-review summary, is available on NTP website. The primary outcomes observed were a small number of cancers of Schwann cells in the heart and non-cancerous changes (hyperplasia) in the same tissues for male rats, but not female rats, nor in mice overall.

Thus far, the data from studies in children with cancer do not support this theory. The first published analysis came from a large case–control study called CEFALO, which was conducted in Denmark, Sweden, Norway, and Switzerland. The study included children who were diagnosed with brain tumors between 2004 and 2008, when their ages ranged from 7 to 19 years. Researchers did not find an association between cell phone use and brain tumor risk either by time since initiation of use, amount of use, or by the location of the tumor (21).
We began by getting a baseline of ambient RF in the room at the location of our testing. We then recorded a baseline of the cellphone RF while on an active call with no case. And finally, we measured the reduction in that baseline (still on the active call) using a variety of different cases and RF reducing products – all at the same set distance from the phone.
Let’s say you are in class, or at the movies, and you don’t want your phone to ring. Slip it into the fully shielded slot. In this position, RF signals in or out will be reduced almost to zero, which is enough to stop the phone from ringing in most circumstances unless you have an especially good connection. You can also store chipped cards (like credit cards) in here to prevent unintentional reading.
Leibovich was very careful to point out in our interview that Cellsafe is not claiming that the radiation absorbed by the body during phone use leads to health issues like brain tumours, male infertility or damage to unborn babies. But the Cellsafe website strongly suggests these links. Its homepage (image below) leads with the phrase "You should be concerned!" in an eye-catching red, and there is as much screen real estate on the site dedicated to information about the dangers of radiation, as there is for descriptions of the Cellsafe products. This information refers to "high levels of RF radiation" in several places, but it doesn't say whether this describes radiation from phone use.
A third requirement was for the FDA to create a formal interagency working group to oversee the work and provide input. The purpose of this was to alleviate any perception that the industry was paying for a result, not for the research itself. But the fourth and last requirement was considered by Dr. Carlo to be highly critical: “Everything needed to be done in sunlight. The media had to have access to everything we did.”
The company's "Researches" page, for example, states that "Aires Technologies are more than 12 years (sic). For this period there have been conducted a number of studies on mechanisms of coherent transformers that effect on physical, chemical, technological and biological processes (sic). The studies were carried out in close collaboration with leading research and academic institutions."
The program began, but Dr. Carlo soon discovered that everyone involved had underlying motives.“The industry wanted an insurance policy and to have the government come out and say everything was fine. The FDA, which looked bad because it didn’t require pre-market testing, could be seen as taking steps to remedy that. By ordering the study, law makers appeared to be doing something. Everyone had a chance to wear a white hat.”

Transmitters, including cell phones, emit radio signals on more than the assigned frequency. These other signals on other frequencies are “harmonics” and/or “noise” and/or “dirty” signals from less than optimal transmitters, antennae, and/or resonating frequencies emitted from metallic objects in close proximity to the transmitter, like the other components of the cell phone.
Another animal study, in which rats were exposed 7 days per week for 19 hours per day to radiofrequency radiation at 0.001, 0.03, and 0.1 watts per kilogram of body weight was reported by investigators at the Italian Ramazzini Institute (35). Among the rats with the highest exposure levels, the researchers noted an increase in heart schwannomas in male rats and non-malignant Schwann cell growth in the heart in male and female rats. However, key details necessary for interpretation of the results were missing: exposure methods, other standard operating procedures, and nutritional/feeding aspects. The gaps in the report from the study raise questions that have not been resolved.