It’s easy to call any case a product designed to block smartphone radiation.  What you need to look for is credible, quantifiable claims that highlight a case’s ability to reduce your exposure to the harmful radiation. Look for relevant  certifications from credible organizations (such as FCC accredited laboratories) that will vouch for product claims, and read product reviews online.

But not everyone is unconcerned. In May 2015, a group of 190 independent scientists from 39 countries, who in total have written more than 2,000 papers on the topic, called on the United Nations, the World Health Organization, and national governments to develop stricter controls on cell-phone radiation. They point to growing research—as well as the classification of cell-phone radiation as a possible carcinogen in 2011 by the International Agency for Research on Cancer, part of the WHO—suggesting that the low levels of radiation from cell phones could have potentially cancer-causing effects.

During the years 1996-1999, due to the sharp increase in mobile phone use, several expert committees convened worldwide to discuss the question whether the radiowave radiation that is emitted from the mobile phone is harmful to health. Their conclusion was that existing scientific knowledge is insufficient to determine the existence or absence of harm to health.
When you talk, your voice is transmitted from the antenna as radio frequency radiation (RFR) between 800 MHz and 2,200 MHz. A range equal to the middle of microwave frequency and 20% to 80% of the radiation emitted is deposited in the user's head. The microwave radiation is absorbed and penetrates the area around the head, some reaching an inch, to an inch and a half into the brain. Exposure to this microwave RFR has shown to have serious health consequences. Laboratory studies have shown that radiation from cell phones expose the user to a wide range of health problems including: 
SAR Shield was developed using the P.A.M. SYSTEM® technology. The materials used in the construction of the SAR Shield attract and dissipate electro-magnetic waves. As radiation travels it uses up its energy. What SAR Shield does is it acts like a radiation magnet, constantly attracting the radiation towards it, therefore making it release its energy closer to the phone. This causes most of the radiation to dissapate away from the head and body. SAR Shield does not cause noticeable reduction in signal strength.
Specifically, we looked for studies that measured rates of acoustic neuromas, gliomas, meningiomas, and thyroid cancers. We also narrowed our search to studies that looked at the effect of radio-frequency radiation originating from an actual cellphone, rather than experimental equipment. We did this because we wanted evidence that could apply to real life, not specific laboratory settings or hypothetical outcomes.

Most cellphone shielding products are designed to reduce radiation to the user while still allowing the phone to function. This means that some radiation can still get to the phone… and some radiation can still get out of the phone! But sometimes you need to completely kill the signal. The RF Kill Box is a full-metal shielding jacket with very high shielding performance.
Yes, the information transferred between the base unit (the phone’s stationary unit) and the wireless phone’s mobile unit is transferred as radiowave radiation. Therefore, the “precautionary principle” should also be adopted regarding wireless phones. In addition to the guidelines regarding mobile phones, the Ministry of Health recommends regarding wireless phones:
Generally speaking, the near-field refers to the RF field close to the antenna and the far-field is the RF field further away from the antenna. Often times when you use your cell phone, your body is often located in the near-field (one wavelength or less) of the cell phone antenna. It is especially concerning when you hold your phone next to your head or wear it on your body as you can be exposed to very intense near-field radiation from the phone.

Limit your (and your children’s) cell phone use. This is one of the most obvious ways to limit your exposure to RF waves from cell phones. You may want to use your cell phone only for shorter conversations, or use it only when a conventional phone is not available. Parents who are concerned about their children’s exposure can limit how much time they spend on the phone.
A large, long-term study has been comparing all of the people in Denmark who had a cell phone subscription between 1982 and 1995 (about 400,000 people) to those without a subscription to look for a possible increase in brain tumors. The most recent update of the study followed people through 2007. Cell phone use, even for more than 13 years, was not linked with an increased risk of brain tumors, salivary gland tumors, or cancer overall, nor was there a link with any brain tumor subtypes or with tumors in any location within the brain.
Bonus application! In addition to shielding magnetic fields, PaperSHIELD is also quite good at shielding radiowaves (cellphone, wifi, etc). And because of the adhesive backing, it can be adhered to almost any surface you need such as the inside or back of your cellphone case. (Use a near field meter to test RF shielding performance.) Note that it is not transparent, so it can't be used on the touch screen side. Cover the cut edges with sturdy tape as they can be sharp. 36 inches wide. Made in USA.
Another way to think about the situation is to consider the steady state power emission of .02 Watts and ask how long it would take to heat up your body by one degree Celsius if your entire volume was exposed. Take your body mass to be 100 kg and approximate it as being composed entirely of entirely of water. If all of the radiation was absorbed and went into heating you up (which it isn’t), it would take 20900000 seconds (specific heat*mass*1 degree/power) or 241 days to heat you up by one degree. Fortunately, you have metabolic processes in your body, or possibly air conditioning, to mitigate this heating.

A few epidemiology studies have reported higher rates of tumors inside the skull among people who use cell phones heavily for 10 years or more. Of particular concern are benign Schwann cell tumors called acoustic neuromas, which affect nerve cells connecting the inner ear with structures inside the brain. These growths can in some instances progress to malignant cancer with time. But other studies have found no evidence of acoustic neuromas or brain tumors in heavy cell phone users.

Who wants to make his own shielded passport or credit card sleeve? Or line a purse, wallet, cellphone case or backpack? Add a shielding liner to a pocket? Wrap a wifi node to block radiation output? Repair a fencing lame? Shield a part of a circuit board? Make an RF gasket? Shield your homeopathy bottles? Attach a ground cord to a fabric? There are hundreds of uses for this versatile shielding patch. A peel-off paper backing reveals a super strong conductive adhesive that keeps the patch where you put it. Easily cut to any shape with ordinary scissors, this metalized fabric is conductive on both sides, completely flexible with no stretch, and solid black in color. 40-50 dB from 10 MHz to 10 GHz. You get two pieces, each 5.5x8 inches. Not intended to adhere directly to skin. Do not machine wash.
* This specification establishes the requirements for heat-sealable, electrostatic protective, flexible barrier materials used for the military packaging of microcircuits, sensitive semiconductor devices, sensitive resistors, and associated higher assemblies. In addition, the type I materials provide for water vapor-proof protection and attenuation of electromagnetic radiation.

In March, however, a peer-review panel of 11 experts from industry and academia voted to advise the agency that it should raise the confidence level from “equivocal evidence” to “some evidence” of a link between cellphone radiation and brain tumors in male rats. (The female rats did not show evidence of a link between the radiation and such tumors.) Two panel members, Lydia Andrews-Jones of Allergan and Susan Felter of Procter & Gamble, proposed the risk upgrade.

 I purchased two different color cases and I was surprised when I received it because the inner case was different than described in some of the reviews. But when I looked at the Amazon listing, I didn’t realize that the case has been updated and I’m pleasantly surprised. The inner case is a soft, flexible plastic that doesn’t seem like it would break at all. I borrowed an EMF reader from a friend and the case works as described. I’m very happy with the cases and I’m glad that I purchased one for my boyfriend too! I definitely recommend this case!
Mobile phones emit radiofrequency energy, a form of non-ionizing electromagnetic radiation, which can be absorbed by tissues close to the phone. The amount of radiofrequency energy a mobile phone user is exposed depend on many factors as the technology of the phone, the distance between the phone and the user, the extent and type of mobile phone use and the user’s distance from cell phone towers. (2)
Cell phones work by sending signals to (and receiving them from) nearby cell towers (base stations) using RF waves. This is a form of electromagnetic energy that falls between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, RF waves are a form of non-ionizing radiation. They don’t have enough energy to cause cancer by directly damaging the DNA inside cells. RF waves are different from stronger (ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light, which can break the chemical bonds in DNA.
Designed to be “leaky”, it permits only a fraction of the RF radiation to penetrate. Exposure to people is reduced (typically 90-99% reduction), and the device usually still works, but with a more limited range. Great for when you permanently or temporarily want to quiet microwave levels without fully turning off the source. Place it over cellphones, cordless phones, two-way radios, smart devices, even wifi routers. Sturdy metal. The two larger units have convenient handle and access holes for wire and cable pass through. Pick the sizes which meet your needs.
Yes, the information transferred between the base unit (the phone’s stationary unit) and the wireless phone’s mobile unit is transferred as radiowave radiation. Therefore, the “precautionary principle” should also be adopted regarding wireless phones. In addition to the guidelines regarding mobile phones, the Ministry of Health recommends regarding wireless phones:
They determined there is “clear evidence” that male rats exposed to high levels of radio frequency radiation — typical of 2G and 3G networks when the study was designed — developed heart schwannomas. There was also “some evidence” of brain and adrenal gland tumors, again in the male rats, but the exposed female rats, and male and female mice, did not have consistent patterns of disease.

A decline in male sperm quality has been observed over several decades.[11][12][13] Studies on the impact of mobile radiation on male fertility are conflicting, and the effects of the radiofrequency electromagnetic radiation (RF-EMR) emitted by these devices on the reproductive systems are currently under active debate.[14][15][16][17] A 2012 review concluded that "together, the results of these studies have shown that RF-EMR decreases sperm count and motility and increases oxidative stress".[18][19] A 2017 study of 153 men that attended an academic fertility clinic in Boston, Massachusetts found that self-reported mobile phone use was not related to semen quality, and that carrying a mobile phone in the pants pocket was not related to semen quality.[20]
The World Health Organization states that "A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use."[2] In a 2018 statement, the FDA said that "the current safety limits are set to include a 50-fold safety margin from observed effects of radiofrequency energy exposure".[3]
The most common effect is heat generation (though non-thermal biological harm has also been demonstrated), which can alter the characteristics of various bodily tissues depending on the amount of radiation present and its ability to penetrate the body. Tissue damage can promote the cellular mutations and increase your long-term risk of developing cancer.
As a good thing to keep in mind, there are hundreds of thousands of people suffering from EHS in the world. Some of them live in forests, tents, and anywhere they can get away from society and EMFs because their symptoms are so bad when exposed. I have not heard one single EHS person claim that any of these types of devices work. They sure don’t for me. Most EHS sufferers are so desperate that they have researched and tried just about everything. Getting away from EMFs, or blocking them with material that does actually block them, like as a Faraday cage, is what works. And this is clearly what the scientific evidence shows. If these devices worked, that would be fabulous. One could spend $100 and be well, instead of having their life turned upside down, and in the worst cases as with some, committing suicide due to complete hopelessness and helplessness.. However, that is not the case. To further prove whether they work or not, one could wear one, and measure with a meter designed to measure EMF absorption in the body (they exist now). Has the manufacturer had this done, and is their evidence of it? An EHS person can tell without a meter anyway, but to prove to others, this might be a good idea.

Because of inconsistent findings from epidemiologic studies in humans and the lack of clear data from previous experimental studies in animals, in 1999 the Food and Drug Administration nominated radiofrequency radiation exposure associated with cell phone exposures for study in animal models by the U.S. National Toxicology Program (NTP), an interagency program that coordinates toxicology research and testing across the U.S. Department of Health and Human Services and is headquartered at the National Institute of Environmental Health Sciences, part of NIH.