Because of this risk of severe reactions with even minute peanut exposures, people with peanut allergy must play a never-ending game of hide and seek with the elusive peanut. Peanuts veil their presence in a surprising number of foods and travel incognito under a host of food label pseudonyms, so you can’t assume that just because a particular dish or food sounds safe, it really is safe.

The brilliant inventor George Washington Carver discovered 300 uses for the peanut. Food manufacturers and cooks have discovered infinitely more uses for peanut, many of which make the peanut nearly impossible to detect. Fortunately, food labeling is conservative, typically warning consumers even if the food “may contain peanuts.” Unlabeled and prepared foods are responsible for a high majority of reactions.

These foods generally fit in one of the two following categories:

• Foods in which you would least expect peanut, such as in sauces and salad dressings, that contain peanut as an ingredient.

• Foods that do not contain peanut as an ingredient but have been contaminated by peanut during production or preparation.

The greatest risk for peanut contaminated foods occurs when other products that do contain peanut are processed or prepared in close proximity to or using the same equipment as the food that you assume is peanut free. This risk is amplified in smaller facilities where the risk of significant cross contamination may be greatest, such as a bakery, restaurant, candy shop, or ice cream parlor.

Of all foods, cookies may well be responsible for the greatest number of accidental peanut exposures. Peanuts pop up in cookies you’d never suspect would contain peanuts, and cookies that are supposedly peanut free often are the victims of cross contamination. Following are some common scenarios that should make you think twice about eating a cookie you haven’t baked yourself:

• A baker decides that a few ground peanuts, a little peanut butter, or even peanut flour would make this batch really special. Because the peanut is pulverized and is used in such small quantities, it’s completely disguised, making detection by sight, smell, or even taste nearly impossible. Pulverized peanuts also find their way into some pie crusts.

• A restaurant serves typically peanut-free chocolate chip cookies. A new cook is hired who always sticks ground up peanuts in the dough to make the cookies a little crunchy. The server assures you that the restaurant’s cookies are peanut free, not knowing that the change of cooks resulted in a change in the recipe.

• The server assures you that a particular brownie doesn’t have peanut in it, but when she dishes up your dessert, she uses the same spatula she used to serve up a dessert that contains peanuts. You may think that the amount of peanut residue would be miniscule, and it is, but it’s enough to cause a severe reaction in some people. Cross contamination may occur when the baker or server uses the same mixing bowl, cookie sheet, spatula, or tongs.

While cookies and similar products carry the greatest risk, all baked goods are suspect. Cakes and cupcakes that seem perfectly safe commonly cause peanut reactions. How can this happen? Cross contamination and hidden ingredients are often the root causes:

• A dirty spatula or other serving utensil: A serving utensil used to serve an unsafe food can sometimes transfer enough of that food to a safe food to trigger a reaction.

• A contaminated knife: A knife used to spread peanut butter icing on one cake and then spread peanut-free icing on your cake or cut your cake can spoil your dessert.

• A flavoring that seems safe: You wouldn’t suspect that something called “Almond Extract” would trigger a peanut reaction unless you’re also allergic to almonds, but I recently saw a girl who had a severe reaction after eating a supposedly safe cupcake a neighbor gave her. It turned out that the particular artificial almond extract the neighbor used was actually made of peanut.

If you’re looking for a tough challenge, mosey down the candy aisle at your local grocery store or pharmacy and try to find candies (especially chocolates) that don’t contain peanuts. Even candy bars that contain no discernable peanuts may have labels that warn people with peanut allergies to avoid them with messages like “May contain peanuts,” “Traces of peanuts,” and “Produced in a facility that uses peanuts.”

Candies produced by major manufacturers are almost always a safe choice, as long as the label does not list peanut as one of its ingredients. By being a diligent, vigilant label reader, you can consume these candies with a very low risk of reaction. The most suspect candies fall into one of the following categories:

• Candy from smaller manufacturers: Watch out for smaller manufacturers who don’t follow strict labeling guidelines or don’t label their candy.

• Unlabeled candies and other goodies: For example, you’d have a tough time finding a safe candy in a fudge or candy shop... or in a gift box from a fudge or candy shop.

• Cross contaminated candies and other goodies, especially from candy or fudge shops: Even if a small candy or fudge shop does not mention peanut on a label, most of these shops have far too much peanut around to successfully prevent cross contamination. I would be very nervous, for example, eating a box of chocolate fudge or chocolate covered cherries, even if the ingredient list contains no hint of peanut.

Stick with candies from major manufacturers, and eat those only after carefully studying the label each time you get them. Another alternative is to purchase candy from one of the guaranteed nut-free candy and baked good manufacturers that have popped up in the last few years. Check out:

• Vermont Nut Free Chocolates (vermontnutfree.com)
• Kellie’s Candies Nut-Free Confections (nutfreecandy.com)
• Rebecca’s Nut Free (rebeccasnutfree.com)
• Nothin’ Nutty (nothinnutty.com)

The rules I described for cookies and candies apply to ice cream, too:

• Stick with ice cream from major manufacturers and carefully read the labels. Although ice cream produced in North America is rarely manufactured on dedicated peanut-free lines, I believe that ice cream from major manufacturers is generally safe.

However, be careful of the small manufacturers — one study a few years ago of small ice cream manufacturers found that peanut contamination was quite common. Allergic reactions to peanut are rarely traced back to cross-contaminated ice cream from the major companies. You can call a company to learn more about how they handle and clean their equipment.

• Make your own ice cream. Some patients decide that the only truly safe ice cream comes from their own ice cream maker in their own kitchen.

• Avoid scooped ice cream from parlors. The ice cream reactions that allergists witness on a regular basis occur with scooped ice cream from ice cream parlors. As with candies and cookies, ice cream from parlors may contain undeclared peanut as an ingredient or, more often, become contaminated from shared ice cream scoops or nearby peanut toppings,

At an ice cream shop, the server typically uses the same scoop for all the flavors, merely rinsing (not washing) it between orders. Once the server opens a container of ice cream and dips into it, you’re likely to be served a scoop of contaminated ice cream.

• Avoid the soft serve parlor, too. Soft serve ice cream resolves the problem of the contaminated scoop, but it’s not a foolproof solution. Most soft serve shops regularly offer a peanut flavor as the flavor of the day. You may arrive at the shop elated to see that strawberry is today’s flavor of the day.

But the shop may be dispensing today’s strawberry ice cream from yesterday’s peanut machine. Soft serve dispensers are extremely difficult to sanitize, and today’s ice cream is almost certainly contaminated by yesterday’s batch.

• Skip the toppings. Almost every ice cream parlor on the planet has a can of chopped peanuts on hand. Watch the servers rush through a couple orders, and you quickly notice that the peanut sprinkles often fly into the chocolate syrup, hot fudge, and other toppings.

Sometimes, the servers use the same spoon to sprinkle on different toppings. Topping dispensers that haven’t been property cleaned and sanitized between flavor changes can also cause problems.

Some resourceful patients bring their own scoop to the ice cream parlor to reduce the risk of cross contamination. However, unless the person behind the counter opens a new tub of ice cream for you to use with your nice clean scoop, this really is not a safe practice.

I do have a few patients with peanut allergy who found local soft serve ice cream parlors where they were comfortable. They know that the chocolate or vanilla machine never handles any other flavor, watch the ice cream come out of the machine and into their cup, and simply avoid toppings altogether.

Just looking at a bowl of chili, you may never guess that any cook worth his wire whisk would consider sticking peanuts in her chili. Flip through a few gourmet cookbooks, however, and you quickly discover that peanut or peanut butter is a pretty standard ingredient.

Cooks may add it to thicken the chili, spice it up with an interesting flavor, or add a little protein in a vegetarian version. The risk of chili became quite well known a number of years ago when a college student at Brown University died after eating chili in a local restaurant.

Hidden peanut can, however, show up in a host of other apparently safe foods, including these:

• Spaghetti sauce: I had never imagined someone sticking peanut butter in spaghetti sauce until I dined on some spaghetti laced with peanut. To find out what happened, check out the sidebar “Who slipped these peanuts into my spaghetti sauce?!”

• Chicken dishes: For some cooks, the marriage of chicken and peanuts is a match made in heaven. For those with peanut allergy, any fancy chicken recipe is suspect. I’ve even seen fried chicken recipes that call for ground peanuts.

• Vegetarian dishes: Without meat, vegetarians have to hunt for their protein elsewhere, and many of them find it in legumes, including peanuts. Be careful around any vegetarian dishes.

The risk of hidden peanut in chili and other dishes is very real and can be life-threatening, but you can protect yourself by following these tips:

• Check with the chef, not only the server. Ask the chef very direct questions and answer any questions the chef has to ensure that your food is safe.

• Always be prepared to deal with a reaction at any time. Immediate treatment is key to your survival and success. No matter how careful you are, you will get burned at some time. Some creative cook will find a new way to use peanuts where you least expect it.

On its surface, my recommendation for peanut oil may sound paradoxically paranoid — most peanut oil is safe, but avoid all peanut oil. Let me clarify that recommendation:

• Highly purified peanut oil is safe. A heat-processed peanut oil is typically completely or nearly completely free of the peanut proteins that trigger reactions. Studies show that these highly purified oils do not cause reactions even in people with severe peanut allergy.

• Cold-pressed peanut oil is dangerous. Because the oil is not heated during processing, it’s raw oil that always contains large amounts of peanut protein.

• Almost all peanut oil is suspect, even peanut oil that’s advertised as peanut-free. In your daily life, you can rarely be sure of the purity of a peanut oil used in preparing your food. To be safe, strictly avoid all forms of peanut oil.

If the world were perfect, discerning which peanut oil is safe and which one is not would be a simple matter of reading the label or talking to the cook. The reality though is that when you look at your bag of potato chips, you’re likely to see peanut oil listed, void of any useful details concerning the purity of that oil.

A few years ago, I ran into a series of peanut oil induced reactions, when a local restaurant chain started serving potato chips fried in cold-pressed peanut oil. Many of the people who reported reactions knew about the peanut oil but had been reassured by the fact that most peanut oils are indeed safe.

They ate the chips thinking that the chips would be okay . . . they weren’t. In my patients I see peanut oil related reactions, including scenarios such as this one, at least once a month. The relative purity of peanut oil makes my rule about avoiding it absolute — avoid all peanut oil.

Follow these tips to remain peanut oil free:

• Carefully read labels and avoid any food that contains peanut oil. Not all peanut oils are created equal.

• Assume that all peanut oil, no matter how it’s processed, contains peanut protein. You just can’t tell how peanut-protein-free any peanut oil is.

• Ask the restaurant manager and cook if peanut oil is used. In most cases, the restaurant manager or cook replies that the restaurant uses “only vegetable oil.” Peanut is a vegetable, so find out the specific ingredients in that vegetable oil.

Don’t panic unnecessarily if your waiter comes out after you have eaten your French fries and says she made a terrible mistake — your fries were really cooked in peanut oil. The risk of any given peanut oil exposure is truly very low. Discuss with your allergist on what to do if such an incident occurs.

When you’re eating in, you can avoid peanuts by following the precautions later. When dining out, however, you must remain even more careful and vigilant to avoid peanuts by following these four steps:

1. Choose a restaurant that is less likely to use peanut in their dishes.
2. Cross off any menu items that are likely to contain peanut.
3. Study the menu carefully to find foods that are more likely to be peanut-free.
4. Confirm that the food you are interested in ordering is indeed safe.

In the following sections, I step you through this four-step process. Follow these same steps if you have a tree nut allergy, keeping in mind that peanuts are more common than tree nuts in American cuisine. More and more restaurants, however, are sprinkling tree nuts over salads and adding them to other menu items.

Vegetarians avoid the local beef house and gravitate toward vegetarian restaurants to take advantage of the expanded selection of vegetarian dishes. Likewise, if you have peanut allergy, you can expand your menu selections by dining at restaurants that offer a wider variety of peanut-free dishes.

Focus on the following types of restaurants:

• Fast food chains: A doctor’s telling you to eat fast food? Well, not exactly, but most large fast-food chains are relatively safe places to eat for people with peanut allergy. The most common risk with fast foods involves the use of peanut oil, especially in the deep fryer.

A number of French fry chains, as well as one national fried chicken chain I can think of, uses peanut oil. Even if you’re eating at a relatively safe fast-food joint, don’t get lulled into a false sense of security. For example, one of the major chains serves a milkshake made with peanut butter candies.

• Steak houses: Your local steak or beef house may be one of the best places to avoid peanuts altogether. These meat-and-potato restaurants commonly serve up pure beef along with potatoes and salads. You still need to be careful about the chef’s secret sauce or barbecue rub and the salad dressings and other items, but a brief conversation with the cook can help you work around these minor complications.

• American cuisine: In the United States, we prefer our peanuts in baked goods and desserts, not in the main course, so restaurants that serve the standard American fare are pretty safe.

• Italian (et tu Pizza): While Italian cuisine may pose an issue for people with tree nut allergy, Italian dishes and pizza are usually safe for those with peanut allergy, although my co-author informs me that he knows of a gourmet pizza joint that serves peanut-butter pizza. Make sure the spaghetti sauce is peanut free.

• Seafood restaurants: As long as you don’t have a seafood allergy in addition to your peanut allergy, seafood restaurants are about as safe as steak houses.

Just because I list a type of restaurant as a safer choice doesn’t mean that it’s 100 percent safe. You still have to perform your due diligence and talk with the server, cook, or restaurant manager each and every time you dine out. Some types of restaurants, particularly those that serve up more exotic cuisine, may be places to avoid:

• Thai: Thai foods probably pose the greatest risk, because so many of the main courses contain peanut.

• Chinese: Chinese foods almost always have at least a few dishes with peanut. Although they’re generally safer than Thai restaurants, Chinese restaurants fall into the same high-risk category.

• Japanese and Korean: Japanese and Korean dishes typically do not call for peanuts, but the cooks often use imported sauces that may contain peanuts or be contaminated with peanuts. Imported products are not held to the same manufacturing and labeling standards as those produced in the United States.

I have some patients who have found Japanese or Korean restaurants where they are completely comfortable eating. However, I personally feel that avoiding these restaurants is the safest option.

• Indian, Pakistani, Afghani, and Napalese: Indian foods often contain peanut and pose a huge risk, although some dishes do not commonly use peanuts and therefore may be safe (except for the possibility of cross contamination). Again, I would avoid all Asian restaurants.

• African, especially Sub-Saharan: African restaurants often serve up peanut soups and a variety of peanut sauces.

• Mexican: While Americanized Mexican food rarely contains peanuts, the same cannot be said for authentic Mexican dishes. Beware of mole sauces, some of which may contain peanut or tree nuts. I do not recommend that you absolutely refrain from Mexican cuisine, but you must certainly approach it with caution.

• Mediterranean and Middle Eastern countries: If you’re doing the Mediterranean Diet or eating out at a Middle Eastern restaurant, you’re generally safe concerning peanuts, but if you’re allergic to tree nuts, too, tread carefully in these foreign eateries. Pine nuts are a common ingredient, and these cultures have found a million and one ways to use pistachios and other tree nuts.

• Health food restaurants: Health food restaurants may serve up cuisine that’s healthier for the general populace, but for those with peanut allergies, these restaurants can pose some hidden risks, especially in vegetarian restaurants, where peanuts are sometimes used to replace meat proteins.

Asian foods are a common source of accidental peanut exposures both because peanut is easily disguised in these dishes and because peanut is used in enough other foods to lead to cross contamination. If the customer before you ordered the Kung Pao chicken, all sorts of peanut remnants can show up in your supposedly peanut-free dish.

This is not just a theoretical concern but rather a very common cause of reactions. I used to eat Asian foods and thought that if I spoke to the chef and ordered carefully I was safe. Luckily, I never had a reaction related to these Asian foods, but the more I get into this field, the more I realize that I was playing a game of Asian roulette.

Some types of prepared dishes have “peanut” written all over them. The following list can help you hone your skills for identifying the riskiest selections:

• Foods with sauces or gravies
• The entire dessert menu, including the ice cream

Whether you’re dining out at a peanut-safe or a peanut-risky restaurant, examine the menu carefully to separate the low-risk from the high-risk items. Highlight the following types of menu items as less risky:

• Simple, straightforward dishes that you would never dream could contain peanuts
• Grilled foods, including chicken, beef, and fish, served with no fancy sauces or gravies
• Pizza and most Italian foods
• Greek foods
• Fried foods, as long as you know the type of oil being used

Low-risk doesn’t mean no-risk. Even if a menu item looks like it can’t possibly contain peanut, you can’t be sure, and you don’t know until you talk with the cook how the item was prepared.

When the server arrives to take your order, make sure that the server talks to the cook directly, or ask to speak with the cook yourself to ensure that your meal not only does not contain peanut as an ingredient but also that the cook prepares it following a peanut-free protocol.

Later, I offer guidance on how to communicate with restaurant personnel no matter what food you’re allergic to, also includes a restaurant card that can provide the cook with additional details without having to step out of the kitchen during the dinner rush.

Before placing your order, explain that you have a severe peanut allergy and that even a trace amount could kill you. Then place your order, as in the following examples:

• “I would like the house salad and the grilled chicken with a baked potato. I need to confirm with the chef that these dishes do not contain any peanut or tree nuts and that contamination with any form of nut cannot occur.”

• “I would like to order a cheeseburger and French fries. I need to know exactly what type of oil is used in your deep fryers.” If the server or cook answers, “We use pure vegetable oil.” Respond with, “I need to know what type of vegetable oil you’re using today.”

Ask the server to be sure to wash his hands before serving your food, just in case he handles another plate between orders that contains peanut residue. However, don’t rely only on the server’s word alone for details about what a particular dish contains. Be sure that the server speaks to the cook about your order and if you have any doubt, speak directly to the cook.