DEAR DR. BLONZ: I was diagnosed with chronic idiopathic urticaria, and it is important that I go on a low histamine diet -- at least, that is what I have read. Is there any guidance that you might provide? There is little information available about histamine in foods. -- S.I., San Jose, California

DEAR S.I.: First, to break down the diagnosis for your fellow readers: Urticaria is a condition that can involve hives and itchy rashes. The "chronic" descriptive means that it is an ongoing condition, as opposed to an itch from an insect bite that annoys and then is history. "Idiopathic" means it's something you have developed and it is unclear why.

The idea of a low-histamine diet is somewhat misleading, because preformed histamine is not found in foods to any appreciable degree. You may not be seeking a diet that is "low in histamine" so much as one that limits foods that tend to trigger a histamine release within body.

Histamine is involved with inflammation, and while we tend to think of inflammation as a bad thing, it is an important element in systems designed to increase blood flow to specific regions. It can also facilitate tissue repairs, the elimination of unwanted substances, and immunological responses to microbiological invaders. The body makes its own histamine from histidine, an essential amino acid; histamine is then stored in "mast cell" reservoirs that are distributed throughout the body.

As can be discerned by the existence of "anti-histamine" products, histamine also has a dark side. It is responsible for the cold- or allergy-like symptoms of sneezing, itchy eyes, runny nose and, in your case, urticaria. Because of these effects, we often turn to antihistamines to provide a measure of symptomatic relief.

A low histamine-producing diet is a quest to identify offending foods. Because histamine is often involved in allergic-type reactions, the first type of food to avoid are those most likely to promote allergies or hypersensitivity reactions, including: shellfish, eggs, cheese, hard sausage, sauerkraut, chocolate, nuts, tomatoes, berries, wine and beer. This would have to be tailored to your situation, and that can mean keeping a log of foods and any untoward experiences related to your condition.

I have also seen lists that say to eliminate food additives such as sulfites, benzoates, nitrites, salicylates, preservatives, artificial colors (especially tartrazines), as well as other foods such as milk, citrus, cola, cinnamon, peas, beans, pork and wheat.

The next foods to consider avoiding are those with unusually high concentrations of "free" histidine. While not an issue with the histidine that is a part of protein, free histidine in foods is a potential problem because there are enzymes that can change this histidine into histamine.

Foods with high levels of free histidine include fish such as tuna, bonito, mackerel, blue marlin, sardines, herring and anchovies. Avoiding these high-histidine foods removes another possible contributor to an increased histamine level in the body.

A study published in the February 2000 issue of the European Journal of Clinical Nutrition found that this strategy has potential: Patients with chronic idiopathic urticaria experienced significant improvement after 21 days on a diet that decreased the types of foods above. Consider consulting with a dietitian to help formulate your strategy.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have concerns about contaminants in fish oil supplements. Is an omega-3 supplement sourced from flax a better alternative? -- F.L., Phoenix

DEAR F.L.: I recommend eating fish over taking fish-oil supplements. Population studies have shown that those with a regular consumption of fish have a lower risk of several chronic diseases, including heart disease, hypertension and certain inflammatory conditions, such as arthritis.

Your question, however, relates to supplements, so let's consider the issue.

The key components are specific omega-3 fatty acids. Fish containing high levels of these include salmon, mackerel, tuna, herring, anchovies, sardines and trout. There are also omega-3 fatty acids in flaxseed and, to a lesser extent, canola and walnut oils, but these are not the same as those found in fish.

To be called an omega-3 means that the first unsaturated bond is on the third carbon of the chain. In fish, we have omega-3s often referred to by their initials: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). They are 20 and 24 carbons long, respectively. The omega-3 in flaxseed and other plant sources is linolenic acid, which is 18 carbons long.

Most people need more omega-3 fats in their diet, whether they come from fish or flax, but there are unique benefits in EPA and DHA.

If you do consume the 18-carbon linolenic acid, your body has the ability to elongate some of it into EPA and DHA, but only a small amount makes it through this process. It is, however, better to have omega-3s from flaxseed than to not have any at all.

Plant sources of omega-3 fats are relied upon by vegans. In addition to fish, EPA and DHA can be found in krill (a crustacean) and in some forms of algae; it is up to the individual to decide the boundaries of their vegan eating plan. I would be remiss if I didn't mention that flaxseed has other health attributes: It is an excellent source of dietary fiber and lignan, a phytochemical that may have anti-cancer effects.

As for pollution, this remains a disturbing topic, and some fish populations have been affected by various contaminants. When eating fish, steer clear of those caught or raised near industrial plants, and stick with those from offshore or deep-sea areas, or from lakes and streams known to be free from harmful chemicals. You might seek guidance from a reputable fish market.

Where supplements are concerned, it is best to check individual products to find one that is free of contaminants. There are processes that allow manufacturers to filter out environmental toxins without affecting the level of the omega-3 fatty acids. Look for an appropriate description on the label stating that the product is contaminant-free. If in doubt, give the manufacturer a call.

One final note: Fish oil supplements should be avoided by those with bleeding disorders and those on anticoagulant medications. Caution is also dictated for those with high blood pressure. Always consult your physician if you have any questions.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: What is the story with having a "sluggish liver"? An article I recently read said that symptoms of a sluggish liver can include having a hard time losing weight, experiencing various abdominal pains or even having cellulite. This piqued my interest, and I found more on the topic, with some articles making specific recommendations for herbs and other dietary supplements. Should I try these treatments? -- F.S., Madison, Wisconsin

DEAR F.S.: The entire concept of a "sluggish liver" has no real medical meaning. I have seen the term used to explain everything from hemorrhoids to migraine headaches. It is difficult to answer the specifics of your question, because to do so would justify your conclusion that a "sluggish liver" was the source of your problems. I cannot help but doubt that this is so.

Our liver is very complex: perhaps the hardest-working and most diverse organ in our body. Its responsibilities include: making our blood; manufacturing proteins; detoxifying chemicals, including alcohol and all matter of drugs and contaminants, whether eaten, injected, absorbed through the skin or present in the air we breathe; making and storing glycogen, a form of stored glucose (blood sugar); turning excess calories into fat for storage; burning fats when necessary; creating ketones when there is insufficient glucose in the blood; producing bile, a substance that helps digest food; storing iron and some other vitamins and minerals; and making the factors that help clot the blood.

The obvious implications of this impressive list is that there can be serious consequences if the liver is not functioning up to par. But what does it mean to have a "sluggish liver"? This nonspecific term is unhelpful. It would be similar to proclaiming "something is wrong," and then expecting this singular confession to give rise to specific advice that will make it right.

With problems involving the liver, the first step should be to determine what's going on. To do this, you'll need to see a health professional, who will take a careful history, do a physical examination and order the appropriate laboratory tests.

Depending on what is at play, it is possible that there might be some treatment that can help, but what works for one individual might be counterindicated for another. The bottom line is that you risk making things worse by trying treatments on your own without knowing the source of the problem, and whether the liver is even involved. I encourage you to take the time to get the needed information before you proceed.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.