Is it safe to plug a power strip into a travel adapter plug?

yes and no.

The adapter does not add any risk or danger, so the answer would be: Yes it is safe.

However, and this applies at home the same, the total power you are pulling through all the plugs in the power strip must not be over the total supported limit, otherwise you will either trip the circuit, or start a fire. Depending on your target country, electrical systems are not always built to handle large power drains, and the circuit tripper might be not working or non-existent. Then it might not be save.

If you use only the usual travel stuff, like cell phone and camera battery chargers and laptop power supplies and such, you probably don’t need to worry. I would not recommend using a hair dryer or space heater through that, though.

There are two types of travel adapter plugs commonly used:

• Plug adapters. These just convert the physical plug into one of a different shape, but do not perform any voltage conversion. It is perfectly fine and common to use one with a power strip (with surge protector). As Aganju points out, you should be careful not to overload any circuits, as a power strip allows you to plug multiple devices into a single outlet. Also, be sure to check that the surge protector is rated to handle the voltage for your destination’s electrical system. Some models are universal, but others may be 110V only and shouldn’t be used in 220-240V electrical systems; check the markings on the device first.

• Voltage converters/transformers. These are somewhat heavy transformers, much larger than a plug adapter, that increase or decrease the voltage of the power to allow it to be used with devices expecting a different voltage than the one locally available. Since many common electronic items carried by travelers are “dual-voltage” or “universal voltage” (they are marked as accepting a wide range of voltages, such as 100-240V), these aren’t as common anymore and may be unnecessary, but are useful if you must travel with a non-universal device. They often include a plug adapter as part of their design.

  Transformers are marked with a maximum wattage that they are capable of handling. Many transformers, especially smaller and cheaper ones, may only handle a load of up to a few hundred watts. It is easy to exceed this limit either with a single high-power device (such as a hair dryer), or a number of lower-power devices. A power strip makes it much easier to overload the transformer.

  EDIT: Here’s a report from someone describing how using a surge protector on the 110V side of a step-down transformer damaged the surge protector and created a safety hazard. Some of this depends on the type of transformer involved, but it’s a good way to try to destroy your surge protector if nothing else. In short: I wouldn’t use a surge protector on the other side of a transformer. A power strip that you are sure has no surge protection wouldn’t have this problem, though just avoiding such setups all together is probably safest.

Personally, I haven’t traveled with a voltage converter (carrying just plug adapters) in years, as I’ve arranged all the electrical devices I take with me to be universal voltage. Converters are heavy and bulky and I prefer to avoid them. Laptops, cell phone chargers, tablets, cameras, etc… are typically universal, though it’s important to check your devices. Some travelers may carry a hairdryer or curling iron, which might not be universal voltage. It is possible to buy special travel models (e.g. from Magellan’s in the US, or a travel supply vendor wherever you are) instead, especially as you’d otherwise need a high-wattage transformer to handle a hairdryer. Or obtain such items in your destination if necessary.

Yes it is safe, a travel adapter is simply a plug and socket built into one piece. Any current the power strip can handle up to circuit breaker tripping can be handled by the adapter.

But you will find in some parts of Asia (Thailand, Cambodia, Laos, Philippines, Vietnam) that sockets take both US style flat blade plugs as well as the European round pins. Japan uses the US style flat blade exclusively, as does Taiwan. So an adapter may not be needed everywhere.